190 BOTANICAL GAZETTE [SEPTEMBER | 
highest powers, but it is by no means necessary to assume that there 
are such. This digression will indicate to some extent, perhaps, the 
viewpoint of the writer in connection with the cytological aspects of 
this work. 
No attempt will be made to discuss here the literature of reduction, 
only a very few of the recent papers being referred to. The discus- 
sion of matters of cytological detail will be taken up at another time. 
One important matter, which was discussed in a former paper (11), 
concerns the method of chromosome reduction, i. e., whether there 
is a pairing of threads about the time of synizesis and whether the 
spirem afterward breaks into a single series or two parallel series 
of chromosomes. In the paper referred to I established the fact 
(as will be conceded, I think, after a study of figs. 20-32, particularly, 
of that paper) that the spirem breaks into a single and not a double 
chain of chromosomes. The possibility of finding a series of stages 
which really demonstrates this depends on the shape of the chromo- 
somes in Oenothera. They are relatively short and thick, like many 
animal chromosomes, and quite unlike the twisted and tangled 
chromosomes of such forms as Lilium, whose relationships are 5° 
difficult to interpret. It is a curious fact that so many of the critical 
studies on reduction in plants have been made on forms with long 
narrow chromosomes, although many of the interpretations of critical 
stages can be made with much greater ease and certainty on forms 
having short and stout chromosomes. 
In the paper just referred to, I concluded that the method was 
probably different in different genera, there being a side-by-side 
pairing of threads in some forms (parasynapsis),° but an end-to-end 
arrangement of the chromosomes to form a single spirem (telo- 
synapsis)° in other forms. Subsequent papers by various invest- 
gators continue to describe both these methods, and the evidence 9 
certain cases is so clear that I think there can remain no doubt that 
both these general methods occur in plants. MONTGOMERY concluded 
in 1898 (26) that there are different types of reduction in animals. 
In a recent study of Fucus, Yamanoucut (39) shows clearly that 
at the time of reduction the ragged nuclear reticulum is gradually 
transformed into a single continuous thread, which enters into 
6 These convenient terms follow the usage of Witson (36). 
