12 MARCUS M. HARTOG. 
Chlamydomonas pulvisculus, with oogamy in the Pero- 
nosporee, and in Gymnosperms and Flowering Plants. 
ITV. CoMPARATIVE GAMETOGENY IN THE VEGETABLE 
Kinepom.! 
I propose now to examine, as completely as materials will 
allow, the types of the modes in which gametes are differ- 
entiated in the vegetable kingdom, from the Protophytes 
upwards. I have not followed any published classification ; 
nor have I aimed at absolute completeness in examples, but 
only in types. 
A. ProtorpHytes AND CELLULAR ALG&. 
Many of the lower types have been treated incidentally in 
the foregoing section, and I need not revert to them. In 
CuztorpHoRACcEz and Unvacrem the zoospores are frequently 
4-flagellate, the isogametes 2-flagellate. This would seem to 
indicate that the segmentation which would otherwise have 
formed zoospores has been pushed a stage further in the for- 
mation of gametes, i.e. that the gametes are formed by the 
bipartition of the nascent zoospores. Multiple union is not 
rare in this group. In several members the conjugation of 
what are supposed to be gametes has not been observed, but 
their nature is a matter of inference from comparison with 
allied forms ; possibly these doubtful gametes are exogamous, 
and could find no suitable mates in the specimens under 
observation. 
To Unorurix I have referred above (p. 9). The formation 
of zoospores and gametes is peculiar: the nuclear divisions are 
completed before the cytoplasm divides; the vacuole becomes 
excentric and peripheral, surrounded by a layer of cytoplasm 
which takes no share in the divisions of the rest of the proto- 
1 I have not confined myself strictly to gametogeny, but have described 
the formation and fate of the zygote wherever it was necessary for the eluci- 
dation of the true character of the gametes. 
