Cytology of the Ascomycetes. 467 
(Figs, ii, 20), but they do not travel towards the poles (Fig. 10). Similar 
radiations are sometimes attached to the nucleolus (Fig. 18). 
Spindle formation and the development of the spores take place 
as in Peziza vesiculosa and will be described in connexion with that 
species. 
PEZIZA VESICULOSA. 
Peziza vesiculosa , Bull. ( Pustularia vesiculosa , FckL), has a conspicuous 
buff apothecium in which the phenomenon of ‘ puffing ’ is well shown. It has 
been studied by a number of observers ; in it Dangeard (7) first saw the 
fusion in the ascus, and it has been more recently investigated by both 
Maire (20) and Guillermond (14). 
The hypothecium is very similar in appearance to that of Otidea 
aurantia but an ascogonium was not recognized. Here also we were unable 
to observe a pseudapogamous fusion. 
We can confirm Maire’ s statement that, before the bending over of the 
crozier, the nuclei in the ascogenous hyphae are not conjugately arranged, 
but we have been unable to recognize with certainty the single division 
which he describes as giving rise to the nuclei destined by a simultaneous 
mitosis to produce the nuclei of the ascus. 
The divisions in the ascogenous hyphae are quite normal (Figs. 21, 22) 
and show about eight chromosomes on the equatorial plate (Fig. 21). 
Afterwards the subterminal cell of the hypha is cut off and gives rise 
to the ascus, as described by Dangeard. In the cases observed by us the 
fusion in the ascus (Fig. 23) took place at about the time of the first meiotic 
contraction. 
The prophases of the first division are not as clearly defined as in 
Otidea ; the regular occurrence, however, of contraction phases (Figs. 24, 
26), as described also by Maire, sufficiently indicates the existence of the 
usual reduction at this stage. 
Guillermond describes the formation of eight chromosomes, the spindle 
being at the same time developed in the centre of the nuclear area. Incur 
material, however, spindle formation took place by the method recorded 
by Harper (15, 19) for Erysiphe and other species. The two centrosomes 
are first observed lying close together (Fig. 27) with a cone of radiations 
passing out from each. A little later, as they move apart, the radiations 
come into contact (Fig. 28) and a spindle is formed. It is at first a good 
deal bent, and is placed across the shorter axis of the nucleus (Fig. 28) ; 
as development proceeds it straightens out and usually comes to lie parallel 
to the longitudinal plane of the ascus (Figs. 29-31). The centrosome 
remains firmly attached to the nuclear membrane, so that the latter is often 
drawn inwards when the spindle is short (Fig. 29). 
In the early stages of division eight chromosomes are visible on the 
