492 Davis . — The Origin of the Archegonhim . 
duced in special regions of the filaments, sometimes con- 
siderably thickened, which resemble the simplest types of 
plurilocular sporangia. The presence of such structures 
among the Chlorophyceae is important, since it tends to 
overcome the difficulties in our assumption of a region of 
extinct green Algae with plurilocular sporangia which we have 
supposed to be the ancestors of the Bryophytes. 
The Rhodophyceae may have arisen close to the Coleo- 
chaetaceae. 
Chaetophoraceae 
l 
Ex’tinct 
Chlorophyceae 
with 
\ plurilocular 
' sporangia 
Ulothricaceae 
Phaeophyceae with 
plurilocular sporangia 
Protococcales 
Fig. 22.' — Diagram showing the position of a hypothetical group of extinct 
Chlorophyceae with plurilocular sporangia, supposed to be the progenitors of the 
Bryophytes, in relation to the algae most intimately concerned with this discussion. 
The lower Phaeophyceae can hardly be supposed to have 
given direct origin to the Bryophytes, although this is con- 
ceivable. They have been arranged at the side of a hypo- 
thetical region of extinct Chlorophyceae. The Fucales are 
far to one side. Their sexual organs are gametocysts, and 
must have had their origin from unilocular sporangia. 
University of Chicago, 
January , 1903. 
