ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
97 
Nuclei of the TTredineae. — From observations on the formation of 
teleutospores in Puccinia Liliacearum , M M. G. Poirault and M. Raci- 
borski * state that the process of karyokinesis in the Uredineae is typically 
that of the higher plants. No reduction in the number of chromosomes 
takes place at the time of the formation of the aecidiospores, spermatia, 
and teleutospores. It follows that the fusion of the nuclei of the teleu- 
tospores cannot be regarded as a sexual phenomenon. The modifications 
in the nucleus which accompany the ripening of the teleutospores of the 
Uredineae, and which are readily observed in Trachyspora Alchemillse y 
correspond altogether to those which take place in the ovules of flower- 
ing plants, with the exception that in the Uredineae there are two nuclei. 
The two nuclei which unite are not always separated ; at a certain 
moment they coalesce, but still behave as two nuclei, each forming two 
chromosomes, a number which has hitherto not been observed in plants, 
and but very rarely in animals. The authors propose to term these 
nuclei conjugated nuclei , and the phenomenon of karyokinesis which they 
exhibit conjugated division. 
To this statement MM. P. A. Dangeard and Sappin-Trouffy reply, j 
asserting that it rests on an error of observation on the part of the 
authors. They have taken the two nucleolated nuclei for a single 
nucleus, the nucleole of which undergoes bipartition ; the two nuclear 
masses of each nucleus were mistaken for the two chromosomes of a 
single nucleus. The “ single nucleus with two chromosomes ” consists in 
reality of two nuclei. They have further seen only one nucleus instead 
of two in the hymenial cells which give birth to the teleutospores. Each 
of these divides normally into two, the first phase in the division being 
marked by an elongation of the nucleus and the disappearance of the 
nuclear membrane. 
In another paper £ MM. Poirault and Raciborski admit the correct- 
ness of some of MM. Dangeard and Sappin-Trouffy’s criticisms, and give 
further details with respect to the development of the aecidiospores and 
of the probasids (teleutospores) in Peridermium Pini acicolum , Puccinia 
Liliacearum , and Coleosporiun Euphrasise. r l he general conclusions 
arrived at are stated as follows : — The multinucleated cells of the 
Uifedinese differ from ordinary multinucleated cells, such as binucieated 
pollen-grains, where the two nuclei are the result of the division of 
a single nucleus. The nuclei of the TJredinese are “ conjugated nuclei.” 
Each nucleus contains only a single chromosome, an instance of 
simple karyokinesis not previously observed in the vegetable kingdom. 
During karyokinesis each nucleus forms two chromosomes. The 
nucleoles have nothing to do with the centrosomes. The principal 
distinction between the conjugated division of the nucleus of the Uredineae 
and ordinary karyokinesis is that the eight, twelve, or twenty-four 
chromosomes (e. g. in the nucleus of the Liliaceae) are surrounded by a 
common protoplasmic mass, while the secondary segments of conjugated 
nuclei remain isolated. The two nuclei which coalesce in the probasids 
(teleutospores) are not sister-nuclei, their origin being very remote from 
one another ; but, since they have the same structure and exhibit the 
* Comptes Bendus, exxi. (1895) pp. 178-80, 308-10. Cf. this Journal, 1894, 
p. 238. t Tom. cit., pp. 364-6 ; Le Botaniste (Dangenrd) iv. (1895) pp. 196-8. 
X Journ. de Bot. (Morot), ix. (1895) pp. 318-24, 325-32, 381-8 (1 pi. and 23 figs.) 
1896 h 
