Fertilization in Collema . 
753 
There are no flask-shaped spermogonia such as have been described for 
other Lichens. The spermatia are simply borne in scattered groups embedded 
in the thallus at a depth of ioo to 300 microns (Fig. 1). They are oval or 
pear-shaped cells, often more or less constricted in the centre (Figs. 2, 4, 
and 5). They are 2 to 3 microns wide and 9 to 12 microns long. They 
stain lightly. There may be few in a group — only two (Fig. 3), or as 
many as fourteen or fifteen may be found in a single cluster. They are 
borne terminally if only one or two are present, or they may be both 
terminal and lateral if more are present. They arise by what appears to 
be a process of budding from certain slender lightly staining hyphae. The 
cells of the hyphae bearing them are often much shorter than the spermatia ; 
sometimes the spermatia are long and narrow. Lindau ( 26 ) has described 
the spermatia of Anaptychia ciliaris as small cells, borne on many-celled 
sterigmata from which they are constricted off. He does not figure them. 
In Collema pulp ostnn, Ach., according to Tulasne, the spermogonia are sunken 
in the thallus and contain many branched septate filaments, the spermatio- 
phores, which bear the spermatia laterally and terminally. In Collema 
cheileum , Ach., the filaments are more branched and the spermogonia not 
sunken in the thallus. In Tulasne’s figure the spermatia are borne at the 
sides and ends of the intercalary cells very much as I find them in my 
material. Tulasne’s figure of C. pulposum shows in some cases two sper- 
matia arising from the same cell. The spermatia of C. jacobaei folium and 
C. pulposum are small oval cells, sometimes constricted in the centre. 
Tulasne ( 35 ) gives the length of the spermatia of C. nigrescens as 4 to 
5 microns. The spermatia of C. microphyllum , according to Stahl, are 
often constricted in the centre ; those of Physma compactum are ovoid. In 
C. crispum , Ach., Baur ( 4 ) found the spermatia to be small ovoidal cells. 
He does not give the size nor tell how they are borne. 
Sometimes the spermatia in my material form such dense groups that 
the exact manner of their origin is difficult to determine. Very commonly 
they are found free, suspended in the jelly of the Nostoc. Apparently when 
mature they are not at all firmly attached to the filament on which they 
are borne. There is no evidence in such sections that they have been torn 
away by the process of fixing and cutting. 
As noted above, the trichogynes in my material do not grow vertically 
upwards to the surface of the thallus, but remain embedded in it, extending 
horizontally or in the plane of the thallus. If we follow them in their 
course the striking fact is at once noted that they grow towards the groups 
of spermatia. In fact, the groups of spermatia are most easily found by 
tracing the long terminal cells of trichogynes which are growing towards 
them. These trichogynes may, of course, run through several sections 
25 microns thick. As one is nearing that section in which the sper- 
matia are present, frequently more and more parts of trichogynes are 
3 D 
