252 BOTANICAL GAZETTE focroser 
zoospores or gametes are finally developed, each in its own compart- 
ment, and this fact makes the group of cells derived from each mother. 
cella sporangium or gametangium. The groups are quite independent 
of one another and there is little hint of a tissue. Essentially the same 
conditions are found in Punctaria. Porphyra is probably very similar 
to Ulva in its methods of spore-formation, whatever may be the signili 
cance of the so-called antherozoids and carpospores. I am impressed 
with the exceeding rarity in the thallophytes, and indeed in all plants, 
of indeterminate regions of gametogenous tissue, and I know of n0 
form that illustrates clearly Miss Lyon’s conception of primitive com 
ditions such as she has tried to illustrate by her diagrams of Ulva. 
Miss Lyon might have made her case appear stronger on fis 
glance by citing Schizomeris and Pylaiella as illustrations of “inde 
terminate masses of reproductive cells.” In these two types the 
sporocyst and sporangium or gametangium: come so close together 
that the general morphology of the respective fruiting filaments ® 
almost identical. The distinctions, however, lie in the presence of very 
numerous cell walls which are never found in sporocysts, and wi 
give the compartment structure to the sporangium and gametanglum. 
The development of cell walls following the segmentation 
protoplasm during sporogenesis may seem a very insignificant facie 
on which to base a broad classification, but I think that close exam 
tion will prove it to be of fundamental importance, because the a 
duction of these walls transforms a reproductive cell i s er 
however simple the arrangement may be. I doubt if tt is ar 
to derive a clearly defined structure from the mere associall 
group of sporocysts or gametocysts, without the cell divisions ™ 
above which immediately change the groups of i appese! 
into sporangia or gametangia. When a number of closely nsf 
ated reproductive mother-cells divide in this manner, the ner 
become quite extensive, and if these cells make up * yee is at 
structure, as perhaps a filament or some emergent region, of these 
once developed an organ. There are abundant illustrations - 
simple conditions, in various stages of relative complexity, 
Phaeosporeae; for example the Ectocarpaceae present @ yee 
from the generalized fruiting filaments of Pylaiella to the 
sporangia and gametangia (plurilocular sporangia) ne 
g 
