EXHIBIT4.2

FORMOFWARRANT

THIS WARRANT HAS NOT BEEN REGISTERED
UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE SECURITIES ACT), OR ANY
STATE SECURITIES LAWS, AND HAS BEEN ACQUIRED FOR INVESTMENT AND NOT WITH A VIEW
TO, OR IN CONNECTION WITH, THE SALE OR DISTRIBUTION THEREOF. NO SUCH SALE OR
DISPOSITION MAY BE EFFECTED WITHOUT AN EFFECTIVE REGISTRATION STATEMENT RELATED
THERETO OR AN OPINION OF COUNSEL, REASONABLY SATISFACTORY TO THE COMPANY, THAT
SUCH REGISTRATION IS NOT REQUIRED UNDER THE SECURITIES ACT.

|Warrant No.:EMP-101(R) | Number of
      Shares:200,000
|---------------------- | ------------------------------

Date of Issuance: March 9, 2000

GERONCORPORATIONCOMMONSTOCKWARRANTAGREEMENT

Geron Corporation (the Company), for
value received, hereby certifies that Eve M. Patton or her registered assigns
(in accordance with Section 3 below) (the Registered Holder), is entitled,
subject to the terms set forth below, to purchase from the Company, at any time
after the date hereof and on or before the Expiration Date (as defined in
Section 6 below), up to 200,000 shares of Common Stock of the Company, as
adjusted from time to time pursuant to the terms of this Common Stock Warrant
Agreement (Warrant), at a purchase price of $17.50 per share. The shares
purchasable upon exercise of this Warrant are hereinafter referred to as the
Warrant Stock. The exercise price per share of Warrant Stock is hereinafter
referred to as the Purchase Price. In connection with the issuance of this
Warrant, the Common Stock Warrant Agreement, Warrant No. EMP-101 has been
canceled.

1.EXERCISE.

(a)MANNER OFEXERCISE. This Warrant may be exercised by the Registered Holder, in whole or in
part, provided that in no event shall partial exercise be for less than 20,000
Warrant Shares, by surrendering this Warrant, with the purchase form appended
hereto asExhibit Aduly executed by such Registered Holder or by such Registered
Holders duly authorized attorney-in-fact, at the principal office of the
Company, or at such other office or agency as the Company may designate,
accompanied by payment in full by cash, check or wire transfer of the Purchase
Price payable in respect of the number of shares of Warrant Stock purchased upon
such exercise.

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(b)EFFECTIVETIME OFEXERCISE. The exercise of this Warrant shall be deemed to have been effected
immediately prior to the close of business on the day on which this Warrant
shall have been surrendered to the Company, with payment of the applicable
Purchase Price, as provided in Section 1(a) above. At such time, the person or
persons in whose name or names any certificates for Warrant Stock shall be
issuable upon such exercise as provided in Section 1(c) below shall be deemed to
have become the holder or holders of record of the Warrant Stock represented by
such certificates.

(c)DELIVERYTOREGISTEREDHOLDER. As soon as practicable
after the exercise of this Warrant, and in any event within ten (10) business
days thereafter, the Company at its expense will cause to be issued in the name
of, and delivered to, the Registered Holder, or as such Registered Holder (upon
payment by such Registered Holder of any applicable transfer taxes) may direct,
a certificate or certificates for the number of shares of Warrant Stock to which
such Registered Holder shall be entitled.

2.CERTAIN ADJUSTMENTS.

(a)MERGERS ANDCONSOLIDATIONS.If at any time there shall be a
merger or consolidation of the Company with another corporation, then, as a part
of such merger or consolidation, lawful provision shall be made so that the
Registered Holder shall thereafter be entitled to receive upon exercise of this
Warrant during the period specified in this Warrant and upon payment of the
Purchase Price, the number of shares of stock or other securities or property of
the Company or the successor corporation resulting from such merger or
consolidation, to which a holder of the Common Stock deliverable upon exercise
of this Warrant would have been entitled under the provisions of the agreement
in such merger or consolidation if this Warrant had been exercised immediately
before that merger or consolidation. In any such case, appropriate adjustment
(as determined in good faith by the Companys Board of Directors) shall be made
in the application of the provisions of this Warrant with respect to the rights
and interests of the Registered Holder after the merger or consolidation to the
end that the provisions of this Warrant (including adjustment of the Purchase
Price then in effect and the number of shares of Warrant Stock) shall be
applicable after that event, as near as reasonably may be, in relation to any
shares or other property deliverable after that event upon exercise of this
Warrant.

(b)SPLITS,SUBDIVISIONS ANDDIVIDENDS.In the event the Company should
at any time or from time to time fix a record date for the effectuation of a
split or subdivision of the outstanding shares of Common Stock or the
determination of the holders of Common Stock entitled to receive a dividend or
other distribution payable in additional shares of Common Stock or other
securities or rights convertible into, or entitling the holder thereof to
receive directly or indirectly, additional shares of Common Stock (hereinafter
referred to as the Common Stock Equivalents) without payment of any
consideration by such holder for the additional shares of Common Stock or Common
Stock Equivalents (including the additional shares of Common Stock issuable upon
conversion or exercise thereof), then, as of such record date (or the date of
such distribution, split or subdivision if no record date is fixed), the per
share Purchase Price shall be appropriately decreased and the number of shares
of Warrant Stock shall be appropriately increased in proportion to such increase
(or potential increase) of outstanding shares.

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(c)COMBINATION OFSHARES.If the number of shares of
Common Stock outstanding at any time after the date hereof is decreased by a
combination of the outstanding shares of Common Stock, the per share Purchase
Price shall be appropriately increased and the number of shares of Warrant Stock
shall be appropriately decreased in proportion to such decrease in outstanding
shares.

(d)ADJUSTMENTCERTIFICATE.When any adjustment is required to be made in the securities issuable
upon exercise of this Warrant, the Company shall mail to the Registered Holder a
certificate setting forth a statement of the facts requiring such adjustment.
Such certificate shall also set forth the kind and amount of stock or other
securities or property into which this Warrant shall be exercisable following
the occurrence of any of the events specified in this Section 2.

3.TRANSFERRESTRICTIONS;REPRESENTATIONS.

(a) The Registered Holder acknowledges that this Warrant and
the Warrant Stock have not been registered under the Securities Act, and agrees
not to sell, pledge, distribute, offer for sale, transfer or otherwise dispose
of this Warrant or any Warrant Stock issued upon its exercise in the absence of
an opinion of counsel, reasonably satisfactory to the Company, that registration
and qualification are not required. Subject to the foregoing, the Company hereby
consents to transfer by the Registered Holder to (i) Noel Thomas Patton, (ii)
the immediate family members (i.e. parents, siblings or children, thereof) of
the Registered Holder or Noel Thomas Patton, or (iii) entities controlled by the
Registered Holder or Noel Thomas Patton or their immediate family members,
provided that the transferee certifies to the Company that it is an accredited
investor as defined in Rule 501 under the Securities Act and agrees to be bound
by the terms of this Warrant. It is understood and agreed that this provision
does not apply to, or limit the sale, pledge, distribution, offers for sale,
transfer or other disposition of Warrant Stock after any exercise thereof
pursuant to Section 1 hereof.

(b) The Registered Holder hereby further represents and
warrants to the Company with respect to the issuance of the Warrant and the
purchase of the Warrant Stock as follows:

(i)PURCHASEENTIRELY FOROWNACCOUNT. This Warrant is issued to the Registered
Holder in reliance upon such Registered Holders representation to the Company,
which by such Registered Holders execution of this Warrant such Registered
Holder hereby confirms, that the Warrant and the Warrant Stock will be acquired
for investment for such Registered Holders own account, not as a nominee or
agent, and not with a view to the resale or distribution of any part thereof,
and that such Registered Holder has no present intention of selling, granting
any participation in, or otherwise distributing the same.

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(ii)KNOWLEDGE ANDEXPERIENCE;ABILITY TOBEARECONOMICRISKS. The Registered Holder has such knowledge
and experience in financial and business matters that it is capable of
evaluating the merits and risks of the investment contemplated by this Warrant
and such party is able to bear the economic risk of its investment in the
Company (including a complete loss of its investment). The Registered Holder is
and will continue to be an accredited investor as defined by Rule 501 of the
Securities Act.

(iii)RESALE. The Registered Holder understands that the Warrant being
issued hereunder and the Warrant Stock to be purchased hereunder are
characterized as restricted securities under the federal securities laws
inasmuch as they are being acquired from the Company in a transaction not
involving a public offering and that under such laws and applicable regulations,
such securities may be resold without registration under the Securities Act only
in certain circumstances. In this regard, the Registered Holder represents that
she is familiar with Rule 144 under the Securities Act, and understands the
resale limitations imposed thereby and by the Securities Act.

(iv)LEGENDS.The Registered Holder
acknowledges that all stock certificates representing shares of stock issued to
the Registered Holder upon exercise of this Warrant may, if such Warrant Stock
is not registered under the Securities Act, have affixed thereto a legend
substantially in the following form:

(x) THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE
SECURITIES ACT OF 1933, AS AMENDED (THE SECURITIES ACT), OR ANY STATE
SECURITIES LAWS. THEY MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED, HYPOTHECATED
OR OTHERWISE TRANSFERRED INTHE ABSENCE OF A REGISTRATION STATEMENT IN EFFECT WITH RESPECT
TO THE SECURITIES UNDER SUCH SECURITIES ACT OR AN OPINION OF COUNSEL
SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED OR UNLESS
SOLD PURSUANT TO AN EXEMPTION TO SUCH SECURITIES ACT.

(y) Any legend required by the laws of any state in which the
securities will be issued.

(c) Subject to the provisions of Section 3(a) hereof, this
Warrant and all rights hereunder are transferable in whole or in part upon
surrender of the Warrant with a properly executed assignment (in the form ofExhibit Bhereto) at the principal office of the Company, provided that in no
event shall such transfer be for less than 20,000 Warrant Shares.

(d) The Company will maintain a register containing the names
and addresses of the Registered Holders of this Warrant. Any Registered Holder
may change such Registered Holders address as shown on the warrant register by
written notice to the Company requesting such change.

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(e) The Company hereby represents and warrants to the
Registered Holder as follows:

(i) The Company is a corporation validly existing and in good
standing under the laws of the State of Delaware.

(ii) The Company has requisite corporate right, power and
authority (including the due authorization by all necessary corporate action) to
enter into this Warrant and to perform its obligations hereunder without the
need for the consent of any other person; and this Warrant has been duly
authorized, executed and delivered and constitutes legal, valid and binding
obligations of the Company enforceable against it in accordance with the terms
hereof. The execution, delivery and performance of this Warrant by the Company
do not contravene or violate any laws, rules or regulations applicable to it.

(iii) The Company has taken such corporate action as is
necessary or appropriate to enable it to perform its obligations hereunder,
including, but not limited to, the issuance, sale and delivery of the Warrant.

(iv) The Warrant Stock, when issued and paid for in compliance
with the provisions of this Warrant, will be validly issued, fully paid and
non-assessable.

4.NOIMPAIRMENT. The Company will not, by amendment of its
charter or through reorganization, consolidation, merger, dissolution, sale of
assets or any other voluntary action, avoid or seek to avoid the observance or
performance of any of the terms of this Warrant, but will assist in the carrying
out of all such terms and in the taking of all such action as may be necessary
or appropriate in order to fulfill its obligations hereunder.

5.TERMINATION. This Warrant (and the
right to purchase securities upon exercise hereof) shall terminate on March 9,
2012 (the Expiration Date).

6.NOTICESOFCERTAINTRANSACTIONS. In the
event that:

(a) the Company shall take a record of the holders of its
Common Stock (or other stock or securities at the time deliverable upon the
exercise of this Warrant) for the purpose of entitling or enabling them to
receive any dividend or other distribution, or any right to subscribe for,
purchase or otherwise acquire any shares of stock of any class or any other
securities or property, or to receive any other right; or

(b) the Company shall effect any consolidation or merger of
the Company with or into another corporation (other than a consolidation or
merger in which the Company is the surviving entity), or any transfer of all or
substantially all of the assets of the Company, or

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(c) the Company voluntarily or involuntarily dissolves,
liquidates or winds-up its business or affairs,

then, and in each such case, the
Company will mail or cause to be mailed to the Registered Holder of this Warrant
a notice specifying, as the case may be, (i) the date on which a record is to be
taken for the purpose of such dividend, distribution or right, and stating the
amount and character of such dividend, distribution or right, and (ii) the
effective date on which such reorganization, reclassification, consolidation,
merger, transfer, dissolution, liquidation or winding-up is expected to take
place, and the record date for determining shareholders entitled to vote
thereon. Such notice shall be mailed at least ten (10) calendar days prior to
the record date or effective date for the event specified in such notice.

7.RESERVATIONOFSTOCK.The Company shall at all times reserve and keep available,
solely for the issuance and delivery upon the exercise of this Warrant, such
shares of Warrant Stock or other stock or securities, as from time to time shall
be issuable upon the exercise of this Warrant.

8.EXCHANGEOFWARRANTS.Upon the surrender by the Registered Holder
of any Warrant, properly endorsed, to the Company at the principal office of the
Company, the Company will, subject to the provisions of Section 3(a) hereof,
issue and deliver to permitted individuals under Section 2.1(g) of that certain
Securities Purchase Agreement, dated as of even date herewith, by and between
the Company and the Registered Holder, at the Companys expense, a new warrant
in a form substantially similar to this Warrant, in the name of such Registered
Holder or as such Registered Holder (upon payment by such Registered Holder of
any applicable transfer taxes) may direct, calling in the aggregate on the face
thereof for the number of shares of Common Stock called for on the face of the
Warrant so surrendered.

9.REPLACEMENTOFWARRANTS.Upon receipt of evidence
reasonably satisfactory to the Company of the loss, theft, destruction or
mutilation of this Warrant and, in the case of loss, theft or destruction, upon
delivery of an indemnity agreement, with surety if reasonably required, in an
amount reasonably satisfactory to the Company, or, in the case of mutilation,
upon surrender and cancellation of this Warrant, the Company will issue, in lieu
thereof, a new warrant in a form substantially similar to this Warrant.

10.MAILINGOFNOTICES.Any notice required or permitted by this Warrant shall be in
writing and shall be deemed sufficient upon receipt, when delivered personally
or by a nationally-recognized delivery service (such as Federal Express or UPS)
or confirmed facsimile, or forty-eight (48) hours after being deposited in the
U.S. mail as certified or registered mail with postage prepaid, if such notice
is addressed to the party to be notified at such partys address or facsimile
number as set forth on the warrant register or as subsequently modified by
written notice.

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11.NORIGHTSASSTOCKHOLDER. Until the exercise of this Warrant, the Registered Holder of
this Warrant shall not have or exercise any rights by virtue hereof as a
stockholder of the Company (including without limitation the right to
notification of stockholder meetings or the right to receive any notice or other
communication concerning the business or affairs of the Company).

12.AMENDMENTORWAIVER.Any term of this Warrant may be amended or waived only by an
instrument in writing signed by the party against which enforcement of the
amendment or waiver is sought.

13.HEADINGS. The headings in this Warrant are for
purposes of reference only and shall not limit or otherwise affect the meaning
of any provision of this Warrant.

14.SUCCESSORSANDASSIGNS. The terms and provisions
of this Warrant shall inure to the benefit of, and be binding upon, the Company
and the Registered Holder and their respective permitted successors and assigns
(in the case of the Registered Holder, in accordance with Section 3(a) hereof).

16.GOVERNINGLAW.This Warrant shall be
governed, construed and interpreted in accordance with the laws of the State of
California, without giving effect to principles of conflicts of law thereof.

| | GERON
      CORPORATION    
| | ---------------------------
| |                            
| |                            
| | By:                        
| |                            
| |                            
| |                            
| |                            
| | Dated:
      April 13, 2009

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EXHIBIT A

PURCHASE FORM

To: GERON CORPORATION

Date:
___________________

The undersigned, pursuant to the
provisions set forth in the attached Warrant, hereby irrevocably elects to
purchase ___________ shares of the Common Stock covered by such Warrant and
herewith makes payment of $___________, representing the full purchase price for
such shares at the price per share provided for in such Warrant.

The
undersigned hereby affirms and acknowledges the investment representations and
warranties made in the Warrant are true and correct as of the date hereof, and
accepts such shares subject to the restrictions of the Warrant, copies of which
are available from the Secretary of the Company.

Signature:
_______________________________________Name: Title: Address:

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EXHIBIT B

ASSIGNMENT FORM

FOR VALUE RECEIVED, _____________________ hereby sells,
assigns and transfers all of the rights of the undersigned under the attached
Warrant with respect to the number of shares of Common Stock covered thereby set
forth below, unto:

|NAME OF
      ASSIGNEE | ADDRESS | No. OF
      SHARES
|---------------------- | ------- | -------------------

Signature:
_______________________________________

Witness:
________________________________________

Dated:
_____________________

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