74 ALTERNATION IN THE THALLOPHYTES 
7 
the 
a development stands hitherto alone,! but biologically it occupies 
same place as a simple sporophyte. 
Fic. 42. 
Coleochacte pulvinata, after Oltmanns. 1, Young zoosporangium (°). Antheridia 
(a) and young oogonium(e). 4, Oogonium shortly before opening. 5, Ditto after opening. 
6, Zygote still with two nuclei, 7, Zygote developed to ‘‘ fruit.” 8, Germinating hypno- 
zygote. a, Antheridium. 0, Oogonium. sk, Male nucleus. e4, Female nucleus. chr, 
Chromatophore. fy, Pyrenoid. 4“, Nucleus. 
Though the cases are thus seen to be still comparatively few in which 
the Thallophytes have had their cytological condition traced throughout 
the whole course of the individual life, there is a growing body of evidence 
to show that an obligatory alternation of cytologically distinct generations 
1Ti is possible that the multicellular spores of Ascomycetes supply a parallel. If, 
as is probable, the reduction accompanies the formation of the ascospores, then the 
subsequent divisions in those spores would hold a similar place in the cytological cycle 
to those in the fruit of Coleochaete. 
