The Pioche weekly record. [volume] (Pioche, Nev.) 1877-1900, 1894-02-22

that the mycelium threads of the lichen
ramify and INTERVENE themselves among
the cells of the bark in the most intimate
manner. The mycelium threads pene-
trate between the cells, loosen them |
from each other and gradually force
them farther and farther apart. The
cells thus come to he imbedded in the !
substance of the lichen, and as the
lichen grows they are carried farther
and farther away from their original
positions. Having removed the super
fetal layers Of cells of the bark, the
lchen attacks those next beneath, and
so on until it penetrates the entire
thickness OF the cOrky layer.
All the superficial cells are surrounded
by the mycelium threads, which have
separated them from each other and are
carrying them out. Farther out can be
seen cells which have been transported
quite distance from their original
situations. Often large groups are sur
rounded by the lichen and drawn up
into its substance. 1t 10 usual TO find
under a large lichen hole through the
entire corky layer, which has been ex-
cavated by this process. This is pro-
badly the cause OF the gap in the layer
of cork.
At a section little to one side of the
middle of the attachment Of lichen, it
can be seen how several layers OF cells are
being carried outward. This stage shows
the beginning OF what subsequently
would become one of the holes through
the cork at the base of the lichen. All
stages can be traced from this con-
dition.
The mycelium acts as a kind OF wedge,
forcing the cells apart and growing
deeper and deeper into the bark. The
cells from the sides of the opening are
being removed at the same time. In a
short time hole would be made here
through the cork as deep as the live
part. A hole having been thus eX-
cavated, it is continually enlarged by
the same process or removing cells.
The base is hollow-it being an old
lichen-and the cells removed from the
middle portion of the excavation do not
appear. Cells are being carried away
from the edges as well as the upper side
of the bark. A large mass OF cells on
the left of the hole is being carried away
entirely. Similar evidence of the re-
moval of cells is to be seen in almost
any section through the base of lichen
What is the Effect of This Removal Of
the Cells of the Bark AN examination
of the tissue below the point Of removal
shows us Enthusiastically that an add.
tional production of cells occurs there
to supply the place OF the bark which
has been removed. 1t also shows us
what invariably occurs whenever the
lichen has penetrated the center bark
We see, then, hole that has been eX
cavated through the regularly arranged
cells of the cork and filled with tn,
mycelium of the lichen. Immediately
under this excavation we can see {
trian ular eminence of cork cells whicl
have been produced there in great abun
dance to fill the gap and have caused tn,
other layers to be tilted up. There ar,
under the edges of the old cork layer
which, being torn away, masses of cell
which are forming to take its place. Tn
break in the bark is not healed, how
ever, for the new formation of cells be
comes stripped off as the old layer wa
taken away. The process of removing
cells and the production OF new one
goes on continuously.
This is a typical illustration OF quit
common state of affairs under lichen
t 1t will be seen that the aggregate thick
ness of the disturbed layers of bark i
much greater than the thickness of tn
, bark on either side. The spaces betw el
these layers are filled by the myceliun
of the lichen, which as they grow pusl
the LAYERS of bark outward. The inter
probation of this section is, think, tina
successive cork layers have been pro
duced and carried out, the new bar
forming as the old is carried away. A
a new layer of cork is formed the myce
way through it, split it off and gradual
push it farther and farther outward.
new layer forms under this and i
carried out in the same manner.
, How the Injury is Done.-The process
, by which lichen Injuries a tree, then
is this: The mycelium threads pervad
the corky layer of the bark, break it IL
and carry the cells outward. As
remedy for this, or, perhaps, as a resul
{ of the unnatural stimulation due to tn
presence Of the mycelium threads, a
extra growth OF cork cells is produced a
the point OF injury. Now, the produC
ton of this additional amount of cor
, cells is plainly a tax upon the vitality c
the tree. In the case of an exceedingl
{ "mossy" specimen where the lichen
t are as thick as they can we'll grow, tn
effect upon the vigor of the tree must b
, great. 1t is common to find in situation
where the air contains much moistur
trees which are simply mass OF lichen
, as far as the new growth. The entir
, bark would be in that case in an ur
| natural and unhealthy condition, and