Cystidia of Coprinus atramentarius. 619 
axes, whilst those which are to become paraphyses expand laterally. Here, 
as in the Coprini generally, the paraphyses have at least two functions : 
(1) they act as spacial agents, in that by their presence they keep the 
basidia so far apart that the spores of neighbouring basidia cannot come 
into contact, and (2) by their gradual expansion they help in bringing about 
the expansion of the pileus. The second of these functions was first 
noticed by Brefeld 1 in his studies of Coprinus stercorarius . During the 
movement of the gills of Coprinus atramentarius from the vertical to 
the horizontal position (cf. PI. L, Figs. 1-4), not a single cell is added to the 
hymenium, and probably none to the subhymenium and trama. The 
elongation of the gill-margins which takes place during this movement 
seems to be entirely due to the expansion of the cells. 
The mode of ripening of the spores and their manner of liberation 
in Coprinus atramentarius is practically the same as that which I have 
described for Coprinus contains. The spores ripen on each gill from below 
upwards. As they ripen, they gradually turn brown in colour, so that in the 
mass they look black. Hence it is that the gills turn black at their bases 
first, and that the blackening progresses upwards on each gill (cf. PI. L, 
Figs. 1-4). 
When the pileus has become expanded to the extent shown in PI. L, 
Fig. 1, the process of spore-discharge begins. The first spores to be dis¬ 
charged are those which are situated in a narrow zone which extends along 
both sides of the extreme lower margin of each gill (s in PI. L, Fig. 2). The 
zone of spore-discharge which has thus come into existence then gradually 
moves upwards on each gill from the bottom to the top. As soon as 
a narrow zone (somewhat less than 0-25 mm. wide) along the bottom of each 
gill has become spore-free owing to spore-discharge, the process of auto¬ 
digestion begins. The cells composing the gills in the spore-free zones 
break down, become fluid, and disappear. This process, which is known to 
mycologists as ‘ deliquescence ’, I have called auto-digestion, 2 for there is 
every reason to suppose by analogy that the gill-tissues are destroyed 
by enzymes which are liberated from the cell-sap of the dying cells. The 
zone of auto-digestion which has come into existence in the manner just 
explained gradually ascends each gill, which thus becomes destroyed from 
below upwards. The zone of auto-digestion follows hard after the zone 
of spore-discharge, but never invades it. It simply involves the zone which 
has become free from spores. After auto-digestion has begun, five zones 
can be distinguished in succession from above downwards on the surface of 
each gill within half a millimetre of, and parallel to, its edge : (1) a zone of 
basidia with ripe spores, (2) a zone of spore-discharge, (3) a zone of spore- 
free surface, (4) a zone of auto-digestion, and (5) a dark adhesive liquid film 
1 O. Brefeld, Untersuchungen, Heft 3, 1887, pp. 64 and 65. 
3 A. H. R. Buller, Researches on Fungi, p. 200. 
