VOLUME LI NUMBER 5 
~ Het 
BOTANICAL GAZETTE 
MAY rgi 
THE MODE OF CHROMOSOME REDUCTION’ 
REGINALD RUGGLES GATES 
In 1894 STRASBURGER (22), in his well-known paper in the 
Annals of Botany, placed the alternation of generations in plants 
on a chromosome basis, and showed that not only does a reduction 
of the chromosomes take place which marks the passage from spo- 
rophyte to gametophyte, but that the reduced or gametophytic 
number is phylogenetically the primitive number, the dominance 
of the sporophyte with the diploid number in the life cycle having 
been reached chiefly in the higher phyla of plants. 
The stimulus to investigation resulting in part from that paper 
has led to two results: (1) the determination, for many members 
of each plant group, of the point in the life cycle where reduction 
occurs; and (2) the detailed investigation of the exact method by 
which the process of chromosome reduction is effected. The 
former line of activity has led to a clear understanding of the life 
cycle in nearly all plants, and is therefore of fundamental signifi- 
cance for plant morphology. The latter line of inquiry has led 
to the expression, during the last fifteen years, of a great variety 
of opinions concerning the precise nature of the reduction process, 
such opinions affecting fundamentally our conceptions regarding 
the nature of the chromosomes themselves and the part they play 
in hereditary processes. These cytological investigations, having 
gone forward simultaneously on plants and animals, have served 
to prove the fundamental unity and universality of meiotic phe- 
nomena in sexual organisms, so that the present-day cytologist 
* The main features of this paper were presented by invitation before the National 
Academy of Sciences, St. Louis Meeting, November 8, 1910. 
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