This fertile branch could easily evolve into an arche- 
onium or an antheridium, or an organ of mixed character. 
But however fascinating and probable a scheme of evolution 
, it deserves scant attention unless it can muster at least cir- 
cumstantial evidence to support it. 
Illustrations of all the phases which 
I have suggested may be readily 
found among the algae, especially 
the browns. Ulva lactuca is a thal- 
lose green alga which consists of two 
layers of cells throughout, except at 
the period of reproduction, when 
‘irregular masses of these cells sub- 
divide into gametes with two cilia, 
a or zoospores with four. Thus in cer- 
tain regions the thallus becomes eight or even ay 
rm 
and mature zoospores of two sizes 
(x, 2). Diagrammatic. 
_ lose body, while the layer of cells on each 
j Surface subdivides into gametogenous or 
_ Sporogenous cells (fig. 13). Punctaria latifolia 
has patches of these cells separated into 
: primitive organs by sterile tissue (fig. 14). : 
4 Moreover, these patches are distinctly of 
on each.—After Ruio- 
CREUX. 
two sorts, the one consisting 
of few large cells, the other 
of small cells which dis- 
charge sperms said to fuse 
: with the larger cells (eggs ?). 
tral Sata latifolia: dorsiven- Zanardinia has exogenous 
on both Sictics. oe ey sex organs of two kinds 
a (fig. 15). The branching of 
the male sex organs is of interest and may suggest a clue to 
that aberration in Anthoceros, Mnium, and the ferns hitherto 
maniey 
TD 
aS Cy 
