Holden and Harper—Nuclear Phenomena. 77 
Sexual reproduction in tlie rusts may possibly dispense with 
cell fusion, while retaining the more essential feature of the 
union of nuclei more or less widely separated in origin. In 
view of the abundant evidence in both plants and animals that 
the fusion of the pronuclei is the more essential element in 
all sexual reproductions, this condition in the rusts is seen to 
be by no means out of harmony with our conceptions of sexual 
reproduction in other groups. Certainly the fusing nuclei of 
Vaucheria or Cysiopu s may be less distantly separated in their 
origin than the fusing nuclei of the rusts and the sexual dif¬ 
ferentiation of the former is unquestioned. The fusing nuclei 
in the zygospores of Spirogyra may be much more closely re¬ 
lated than those in the rusts. That the fusion of nuclei con¬ 
tained in the same mass, of cytoplasm for a long series of nu¬ 
clear generations, hay have the same effect for the cell in which 
they are contained, as results from ordinary fertilization is, 
however, a distinctly new idea and must modify our conceptions 
correspondingly. As pointed out above, it emphasizes still fur¬ 
ther the doctrine that nuclear rather than cytoplasmic fusion 
G the essential process of fertilization. 
Index of Literature. 
1. Sappin-Trouffy. Becberches histologiques sur les Uredi¬ 
nees. Le Botaniste, ser. 5, 1896. 
2. Dangeard, P. A., and Sappin-Trouffy. Besponse a une 
note de M. M. G. Poirault et M. Baciborski. Le 
Botaniste, ler aout 1895. 
8. Poirault, G., and Baciborski, M. Sur les noyeaux des 
Uredinees. Journ. de Bot. tom. IX. 1895. 
4. Dangeard, P. A, and Sappin-Trouffy. Une pseudo-fecon- 
dation c-hez les Uredinees. Comptes Bendus T'. 16, 
p. 257. 
5. Baciborski, M. Ueber den Einffuss ausserer Bedingungen 
auf die Wachthumsweise des Basidiobolus ranarum. 
Flora. 1896. 
