466 BOTANICAL GAZETTE [DECEMBER 
internuclear aster appear, these protochromosomes leave the achromatic substance, 
being attracted about four centers to form the four definite chromosomes. Fac 
of the four definite chromosomes undergoes a longitudinal fission, the two halves 
of which separate at the metaphase, undergoing a new longitudinal splitting 
during their passage to the poles. This second split is often very distinct during 
the anaphase of this division, when eight chromosomes may be counted. Durin 
the prophases of the second division eight chromatic elements reappear, which 
unite two and two to form the definite chromosomes of the equatorial plate. The 
two halves of each chromosome separate, four passing to each pole. e first 
division of the ascus Marre believes therefore to be preceded by a true synapsis, 
very similar to that described by StRASBURGER for Thalictrum purpurascens. 
He believes the protochromosomes should be interpreted as the gamosomes of 
STRASBURGER. The segregation and re-collection of the chromatin of two primary 
nuclei assures a complete rearrangement of the chromatin in the definite chro- 
mosomes of the secondary nucleus. Marre designates the fusing nuclei as pri- 
mary and the resulting fusion nucleus or ascus nucleus as secondary. These 
phenomena, together with the longitudinal splitting preceding the metaphase of 
the first division, and the longitudinal fission during the metaphase of the second 
division, which split is much more complete than in phanerogams, all show that 
the first mitosis in the ascus is heterotypic, analogous to the first division of all 
normal spore mother-cells, while the characters presented by the second mitosis 
are those of a homotypic division. Marre further believes that the third division 
is a typic one, where the spirem directly segments into the four chromosomes, 
which only divide at the metaphase. The proof that the first division in the ascus 
is heterotypic certainly favors the view that the numerical reduction of chromo- 
somes occurs immediately after the fusion which produces the nucleus of the 
ascus. This hypothesis finds support in the fact that the number of chromosomes 
in the mitoses in the ascus and in the ascogenous hyphae is the same as in Pyro- 
nema. MatrE has not been able to count the chromosomes of the ascogenous 
hyphae. He admits the fact that the number of chromosomes may vary in 
different species of the Ascomycetes, just as this number varies in higher plants, 
instead of being always four as he has previously maintained. In Galactinia 
succosa the centrosomes and the spindle have an intranuclear origin, while the 
polar radiations have an extranuclear origin, developing independently of the 
intranuclear part of the achromatic figure. The ascus presents the cytological 
characters of secreting cells. In the epiplasm are found basiphile granules 
entirely distinct from the metachromatic granules, and often a sort of latex. The 
nucleus is able to take an active part in the elaboration of certain secretory 
products.—J. B. OvERToN. 
A RECENT paper by FiscHER"™ on the Cyanophyceae, while reaffirming in 
the main his earlier conclusions,'s presents some further additions to the cytology 
14 FISCHER, A., Die Zelle der Cyanophyceen. Bot. Zeit. 63": 51-130. pls. 2. 1905. 
"Ss FiscHEer, A., Untersuchungen iiber den Bau der Cyanophyceen und Bakterien. 
Jena. 1897. ; 
