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                                                                     EXHIBIT 4.4

NEITHER THIS WARRANT NOR ANY SHARES OF COMMON STOCK ISSUABLE UPON THE EXERCISE
OF THIS WARRANT HAVE BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED, AND THE RULES AND REGULATIONS PROMULGATED THEREUNDER (THE "SECURITIES
ACT").  THIS WARRANT AND THE COMMON STOCK ISSUABLE UPON EXERCISE OF THIS WARRANT
MAY NOT BE OFFERED, SOLD, OR OTHERWISE TRANSFERRED IN THE ABSENCE OF
REGISTRATION  UNDER THE SECURITIES ACT OR SUCH OFFER, SALE OR TRANSFER IS EXEMPT
FROM SUCH REGISTRATION.

                   COMMON STOCK PURCHASE WARRANT CERTIFICATE
                   -----------------------------------------

                          Dated:  [Month] ____, 1996

                             [Number ( )] Warrants

                        to Purchase [Number ( )] Shares

                  of Common Stock, $0.10 Par Value Per Share

          [COMPANY], a [State] corporation (the "Company"), hereby certifies
that [Holder], its permissible transferees, designees, successors and assigns
(collectively, the "Holder"), for value received, is entitled to purchase from
the Company at any time commencing on [Month]   , 1996 up to [Number] ( ) shares
                                              --                                
(the "Shares") of the Company's common stock, par value $0.10 per share (the
"Common Stock"), at [$_____] per share (the "Exercise Price").

          1.  Exercise of Warrants.  Upon presentation and surrender of this
              --------------------                                          
Common Stock Purchase Warrant Certificate ("Warrant Certificate" or "this
Certificate"), with the attached Purchase Form duly executed, at the principal
office of the Company at [address], together with a check payable to the Company
in the amount of the Exercise Price multiplied by the number of Shares being
purchased, the Company, or the Company's Transfer Agent as the case may be,
shall deliver to the holder hereof, certificates of Common Stock which in the
aggregate represent the number of Shares being purchased.  All or less than all
of the Warrants represented by this Certificate may be exercised and, in case of
the exercise of less than all, the Company, upon surrender hereof, will deliver
to the holder a new Warrant Certificate or Certificates of like tenor and dated
the date hereof entitling said holder to purchase the number of Shares
represented by this Certificate which have not been exercised and to receive
Registration Rights with respect to such Shares.

          In lieu of tendering the requisite Exercise Price to the Company in
cash, the Holder may elect to exercise this Warrant Certificate on a net basis
whereupon (a) the number of shares of Common Stock issued upon such exercise
shall be reduced by that number of shares which have an aggregate fair market
value, based upon the average closing price for the Company's Common Stock for
the three trading days preceding the Exercise Date, equal to the requisite
aggregate Exercise Price and (b) the Exercise Price shall be deemed to have been
paid and satisfied by the tender of such shares to the Company.

          2.  Exchange and Transfer.  This Certificate at any time prior to the
              ---------------------                                            
exercise hereof, upon presentation and surrender to the Company, may be
exchanged, alone or with other Certificates of like tenor registered in the name
of the same holder, for another Certificate or Certificates of like tenor in the
name of such holder exercisable for the aggregate number of Shares as the
Certificate or Certificates surrendered.

          3.  Rights and Obligations of Holders of this Certificate.  (a)  The
              -----------------------------------------------------           
Holder of this Certificate shall not, by virtue hereof, be entitled to any
rights of a stockholder in the Company, either at law or in equity; provided,
however, that in the event any certificate representing shares of Common Stock
or other securities is issued to the holder hereof upon exercise of some or all
of the Warrants, such holder shall, for all purposes, be deemed to have become
the holder of record of such Common Stock on the date on which this Certificate,
together with a duly executed Purchase Form, was surrendered and payment of the
aggregate Exercise Price was made, irrespective of the date of delivery of such
share certificate.

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Common Stock Purchase Warrant Certificate

Page 2


          (b)  In case the Company shall (i) pay a dividend in Common Stock or
make a distribution in Common Stock, (ii) subdivide its outstanding Common Stock
into a greater number of shares, or (iii) combine its outstanding Common Stock
into a smaller number of shares (including a recapitalization in connection with
a consolidation or merger in which the Company is the continuing corporation),
then (x) the Exercise Price on the record date of such division or the effective
date of such action shall be adjusted by multiplying such Exercise Price by a
fraction, the numerator of which is the number of shares of Common Stock
outstanding immediately before such event and the denominator of which is the
number of shares of Common Stock outstanding immediately after such event and
(y) the number of shares of Common Stock for which this Warrant Certificate may
be exercised immediately before such event shall be adjusted by multiplying such
number by a fraction, the numerator of which is the Exercise Price immediately
before such event and the denominator of which is the Exercise Price immediately
after such event.

          (c)  In case of any consolidation or merger of the Company with or
into another corporation (other than any consolidation or merger in which the
Company is the continuing corporation and which does not result in any
reclassification of the outstanding shares of Common Stock or the conversion of
such outstanding shares of Common Stock into shares or other stock or other
securities or property), or the sale or transfer of the property of the Company
as an entirety or substantially as an entirety, there shall be deliverable upon
exercise of the Warrant Certificate (in lieu of the number of shares of Common
Stock theretofore deliverable) the number of shares of stock or other securities
or property to which a holder of the number of shares of Common Stock which
would otherwise have been deliverable upon the exercise of this Warrant
Certificate would have been entitled upon such action if this Warrant
Certificate had been exercised immediately prior to such action.

          4.  Common Stock.  (a)  The Company covenants and agrees that all
              ------------                                                 
shares of Common Stock issuable upon exercise of this Warrant Certificate will,
upon delivery, be duly and validly authorized and issued, fully-paid and non-
assessable.

          (b)  The Company covenants and agrees that it will at all times
reserve and keep available an authorized number of shares of its Common Stock
and other applicable securities sufficient to permit the exercise in full of all
outstanding options, warrants and rights, including the Warrants.

          5.  Registration Rights.  In the event the Company files a
              -------------------                                   
Registration Statement with the Securities and Exchange Commission for
registration of any shares of the Company's Common Stock, the Company agrees to
include the number of shares of Common Stock represented by this Warrant
Certificate in any such Registration Statement.

          6.  Issuance of Certificates.  As soon as possible after full or
              ------------------------                                    
partial exercise of this Warrant, but in any event not more than three (3)
business days, the Company, at its expense, will cause to be issued in the name
of and delivered to the holder of this Warrant, a certificate or certificates
for the number of fully paid and non-assessable shares of Common Stock to which
that holder shall be entitled on such exercise.  No fractional shares will be
issued on exercise of this Warrant.  If on any exercise of this Warrant a
fraction of a share results, the Company will pay the cash value of that
fractional share, calculated on the basis of the Exercise Price.  Prior to
registration of the shares of Common Stock underlying this Warrant Certificate,
as provided in Section 5 hereof, all such certificates shall bear a restrictive
legend to the effect that the Shares represented by such certificate have not
been registered under the Securities Act of 1933, as amended, and the Shares may
not be sold or transferred in the absence of such registration or an exemption
therefrom, such legend to be substantially in the form of the bold face language
appearing on Page 1 of this Warrant Certificate.

          7.  Disposition of Warrants or Shares.  The holder of this Warrant
              ---------------------------------                             
Certificate, each transferee hereof and any holder and transferee of any Shares,
by his or its acceptance thereof, agrees that no public distribution of Warrants
or Shares will be made in violation of the provisions of the Securities Act of
1933, as 

                                       2
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Common Stock Purchase Warrant Certificate

Page 3

amended, and the rules and regulations promulgated thereunder (collectively, the
"Act"). Furthermore, it shall be a condition to the transfer of the Warrants
that any transferee thereof deliver to the Company his or its written agreement
to accept and be bound by all of the terms and conditions contained in this
Warrant Certificate.

          8.  Notices.  Except as otherwise specified herein to the contrary,
              -------                                                        
all notices, requests, demands and other communications required or desired to
be given hereunder shall only be effective if given in writing by certified or
registered mail, return receipt requested, postage prepaid, or by U. S. express
mail service or private overnight mail service (e.g. Federal Express).  Any such
notice shall be deemed to have been given (a) on the business day immediately
subsequent to mailing, if sent by U. S. express mail service or private
overnight mail service, or (b) three (3) business days following the mailing
thereof, if mailed by certified or registered mail, postage prepaid, return
receipt requested, and all such notices shall be sent to the following addresses
(or to such other address or addresses as a party may have advised the other in
the manner provided in this Section 8):

          If to the Company:

          [Name]

          [Address]

          If to the Holder:

          [Name]

          [Address]

          9.  Governing Law.  This Warrant Certificate and all rights and
              -------------                                              
obligations hereunder shall be deemed to be made under and governed by the laws
of the State of California without giving effect to the conflicts of laws
provisions.  The Holder hereby irrevocably consents to the venue and
jurisdiction of the State and Federal Courts located in the State of California,
County of Marin.

          10.  Successors and Assigns.  This Warrant Certificate shall be
               ----------------------                                    
binding upon and shall inure to the benefit of the parties hereto and their
respective successors and assigns.

          11.  Headings.  The headings of various sections of this Warrant
               --------                                                   
Certificate have been inserted for reference only and shall not be a part of
this Certificate.

          IN WITNESS WHEREOF, the Company has caused this Warrant Certificate to
be duly executed, manually or by facsimile, by one of its officers thereunto
duly authorized.

                              [COMPANY]

                              Date:
                                   -----------------

                              By:
                                 ------------------------------------

                              [Name and Title]

                                       3
<PAGE>
 
                             ELECTION TO PURCHASE
                             --------------------

To Be Executed by the Holder

in Order to Exercise the Common Stock

Purchase Warrant Certificate

          The undersigned Holder hereby irrevocably elects to exercise
                                                                       -------
of the Warrants represented by this Common Stock Warrant Certificate, and to
purchase the shares of Common Stock issuable upon the exercise of such Warrants
and requests that certificates for securities be issued in the name of:

          -------------------------------------------------------

           (Please type or print name and address)


          -------------------------------------------------------

          -------------------------------------------------------

          -------------------------------------------------------

          (Social Security or tax identification number)

          and delivered to
                           --------------------------------------

          -------------------------------------------------------

          (Please type or print name and address

          and, if such number of Warrants shall not be all the Warrants
evidenced by this Common Stock Warrant Certificate, that a new Common Stock
Warrant Certificate for the balance of such Warrants be registered in the name
of, and delivered to, the Holder at the address stated below.

          In full payment of the purchase price with respect to the Warrants
exercised and transfer taxes, if any, the undersigned hereby tenders payment of
$           by check or money order payable in United States currency to the
 -----------                                                                
order of [Company].

          [HOLDER]

          Dated:                    By:
                -------------------   ---------------------------------

             Name:

             Title:
                   -------------------------------------------------------


          
          (Address)

          -------------------------------------------------------

          -------------------------------------------------------

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Common Stock Purchase Warrant Certificate

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          (Social Security or tax identification number)

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