Eumycetes. 
467 
from different nuclei while in the second „such a contraction does 
not appear and the Separation of entire chromosomes takes place.” 
The meiotic reduction no doubt compensates for the fusion which 
corresponds to the sexual fusion, while the brachymeiotic reduction 
compensates for the asexual fusion in the ascus. It is suggested 
that when once the second reduction had become established the 
ascus-fusion would be a necessary eorollary, and so one may per- 
haps, account for the extraordinary regularity of the occurrence of 
this fusion in the group. No pairing of nuclei was observed in the 
ascogenous hyphae. The spore is delimited by radiations from 
the centrosome, though near the base of the spore the walls of va- 
cuoles may take part in the process. V. H. Blackman. 
Fraser, H. C. J. and E. T. Welsford, Further contributions 
to the Cytology of the Ascomycetes. (Annals of Botany. XXII. 
p. 465—477 with 2 plates. 1908.) 
In continuation of Miss Fraser’s earlier work on Humaria ruti- 
lans the authors have investigated the reduction processes in the 
ascus of Otidea aurantia Mass. and Peziza vesiculosa Bull. They 
find that these two species resemble the first named form in that 
there is a double reduction in the ascus. The first two divisions 
constitute an ordinary meiotic phase, the details of reduction cor- 
responding closely with those discussed by Farmer and Moore for 
the higher plants and animals. The third division constitutes a bra- 
chymeiosis, the most essential feature of which is that half the 
chromosomes pass to opposite poles without any Splitting. The ar- 
rangement of the chromosomes in this division is different in different 
forms. They may be independent as in H. rutilans\ they may be 
paired at the beginning of the division as in 0. aurantia, or at an 
earlier stage as in P. vesiculosa and in Phyllactinia. A table is 
given which elucidates clearly the relation of the chromosomes in 
the various forms which have been investigated. 
In O. aurantia and in P. vesiculosa the forming in the third di¬ 
vision is associated with a contraction phase. This leads the authors 
to the view that the difference between meiosis and brachymeiosis 
lies in the possession of a meiosis of the second (synaptic) con¬ 
traction, while brachymeiosis may or may not exhibit the first con¬ 
traction of Farmer and Moore. The Statement is made that „it 
seems not unlikely that the synaptic phase indicates the moment of 
some interchange of material between the already paired allelo- 
morphs.” It was found that in 0. aurantia fusion in the ascus „oc- 
curs at about the time of the first meiotic contraction, the two nuclei 
thus starting this process independently. It is pointed out that these 
observations of the double reduction in the ascus together with the 
observations on the mildews are impossible to reconcile with Claus- 
sen’s generalization as to the existence of only one nuclear fusion, 
that in the ascus, throughout the Ascomycetes. 
Observations, especially those on P. vesiculosa show that the 
spores are delimined to some extent by vacuoles but mainly by the 
astral rays. „It is suggested that these may represent the paths of 
activity of an enzyme generated by the centrosome and producing 
Chemical changes in the surrounding cytoplasm. 
V. H. Blackman. 
