The Origin and Development of the Apothecium etc. 
407 
growth of trichogynes toward sperraatia and the coiling of the trichogyne 
tip around the spermatium in C. pulposum makes it possible to change 
Baur’s word “unwahrscheinlich” to “unmöglich”. In lichens whose 
trichogynes protrude and are completely passive it must be more or 
less a matter of accidcnt that spermatia reach the trichogyne through 
the agency of rain or wind. It may be too that the gelatinous substance 
on the protruding tip of the trichogyne contains some substance which 
supplies a Chemical Stimulus that causes the spermatia, when rain has 
brought them within ränge of perception of this Stimulus, to reach 
the trichogyne. The spermatia of lichens are always regarded as non- 
motile cells. But if there is a gelatinous or sticky sheath of material 
surrounding the tip of the trichogyne, the spermatium must move or 
be moved through this if there is to be a fusion of the cells. Excepting 
at the extreme tip of the trichogyne, Baur has figured this sticky sheath 
from half to l 1 / 2 times the thickness of the spermatium. It is not with 
the extreme tip of the trichogyne that the spermatium fuses, to judge 
from Baur’s and Stahl’s figures, but with the side of the trichogyne at 
a point some little distance from the tip — where, therefore, the sheath 
is thickest. Hence there must be some means for bringing these walls 
in contact. 
Changes in the Trichogyne following fusion with a Spermatium. 
After fusion with a spermatium the protruding cell of the trichogyne 
in C. microphyllum (Stahl, 74) collapses and becomes a formless mass. 
I do not find that the distal end of the trichogyne in C. pulposum is that 
which first collapses, but rather that the long terminal cell may collapse 
at various points. The gelatinization of the cross walls of the lower cells 
of the trichogyne as I have described it agrees very well with the aecounts 
of Stahl and Baur for the forms they studied. In C. pulposum these 
thickened plugs are most often biconvex although they may be biconcave. 
In C. microphyllum they are usually convex, in Plnjsma compactum usually 
eoncave. The most distal of these cells may become separated by the 
Separation of the gelatinous plug along the plane of the original septum 
into two parts. In my material, as in other Collemas, this gelatiniza- 
tion begins at the most distal septum and progresses toward the ascogone. 
The thickening is also least nearest the ascogone, and here the cross walls 
are very plainly perforated. Baur says that this Perforation of the 
trichogyne cross walls makes it very probable that a relativelv firm body, 
likely the spermatium nucleus, has migrated through the septa. I have 
sliown that this Perforation of the walls of the trichogyne and also pro- 
