No. 463.] STUDIES ON PLANT CELL.— VI. 475 
expressed it ('94a, p. 288), a return on the part of the plant 
organism in each life history to the condition of an ancestral sex- 
ual generation (gametophyte). Reduction phenomena in them- 
selves are not the result of a gradual evolution, whatever may 
be the complicated history of the sporophyte generation, for 
they consist always in the sudden reappearance of the primitive 
number of chromosomes, characteristic of the generation in 
which sex arose (gametophyte). The cause of reduction phe- 
nomena is phylogenetic. The interval that may separate this 
phenomenon from the responsible sexual act varies immensely in 
the plant kingdom according to the evolution of the groups con- 
cerned. But the suddenness of the appearance of sporogenesis 
tells in every case the same story of an immediate and total 
change in the potentialities of the protoplasm in the spore 
mother-cell, a change which can only be understood as a phylo- 
genetic process deeply seated in the race. 
When the events of sporogenesis in plants are considered as 
processes of spermatogenesis or oógenesis we disregard the most 
remarkable historic outlines that plant phylogeny can present, 
to the confusion of clear thought. Botanical science may well 
be proud of its achievement in outlining with such exactness the 
relations that the critical periods of gametogenesis, fertilization, 
. and sporogenesis bear to reduction phenomena and too great 
stress can hardly be laid upon the importance of the results. 
4. REDUCTION OF THE CHROMOSOMES. 
There are perhaps no activities of the cell which have been 
the subject of more investigation and discussion than those of 
chromosome reduction in animals and plants. The reasons are 
clear. The events of gametogenesis in animals and of sporogen- 
esis in plants have the deepest significance for an understanding 
of the organization of protoplasm because these are periods when 
great changes are made evident in the structure of e cells con- 
cerned and at the same time in their potentialities. We are 
forced to conclude that some of the structural changes at least 
are the cause of the new potentialities and the attempt to estab- 
lish the cause and effect has been one of the most fruitful and 
