Observations on the Biology and Cytology of 
a new variety of Achlya americana. 
BY 
A. H. TROW. 
With Plates VIII-X. 
H ARTOG’S (’95) paper ‘ On the Cytology of the Vegeta- 
tive Organs of the Saprolegnieae,’ and my observations 
on ‘ The Karyology of Saprolegnial (’95), appeared almost 
simultaneously. Hartog ( 5 96) shortly afterwards published 
a brief criticism of my results, in which he expressed the 
view that all the species of the Saprolegnieae, or at any 
rate those examined by me, must have four chromosomes, 
and so conform to the case or cases investigated by himself, 
a view which one would hardly expect from an observer of 
such wide and varied knowledge and keen critical faculty ; 
and it is even more remarkable to find that Zimmermann 
(’96), who, however, had not seen Hartog’s paper, appears 
inclined to adopt it. One would imagine that the well- 
known case of A scar is meg aloe ephala, in which there are 
two varieties distinguishable only by the difference in the 
number of the chromosomes, would in itself be sufficient 
to indicate the fundamental weakness of such a criticism. 
The evidence furnished by the Liliaceae shows clearly enough 
that the number of chromosomes may vary not only from 
species to species, but even in the cells of the same individual. 
[Annals of Botany, Vol. XIII. No. XLIX. March, 1899.] 
K 2 
