626 
Butter .— The Function and Fate of the 
are found, if such there are, in which there is no auto-digestion whatever, I 
think we should regard auto-digestion of the gills as one of the most 
constant and general of all the characters of Coprinus species. 
In a former publication I contrasted the Mushroom and the Coprinus 
types of fruit-bodies as represented by Psalliota campesiris on the one hand 
and by Coprinus comatus on the other. However, since making that con¬ 
trast, I have realized that it was incomplete. I omitted to mention two 
quite general and, as it seems to me, fundamental points of difference 
between the gills of Coprini and of all other Agaricineae, which I have only 
realized during my more recent and extended studies. In the Coprini the 
gills are: (1) relatively very thin, and (2) parallel-sided, whereas in fruit- 
bodies of the Mushroom type the gills are: (1) relatively very thick, and 
(2) have their sides inclined to one another like the sides of a penknife. It 
seems to me that the extreme reduction in gill-substance in the Coprini has 
necessitated that the two sides of each gill should be parallel, and it also 
seems to me that the ripening and discharge of the spores from below 
upwards on each gill, together with the gradual auto-digestion of the spore- 
free portions of the gills from below upwards, are special adaptations which 
permit of successful spore-liberation from parallel-sided gills. In wedge- 
shaped gills, on the other hand, such as occur in Psalliota campestris , &c., 
the two gill-sides look slightly downwards. In this type of gill every 
square millimetre of gill-surface can successfully shed a certain number 
of spores every minute (or other unit of time) during the whole period 
of spore-discharge. Hence with wedge-shaped gills there is no need for the 
spores to ripen and be discharged in succession from below upwards on each 
gill, and no need for auto-digestion. A fuller statement and analysis of the 
facts of the comparative morphology of the Agaricineae in relation to the 
production and liberation of spores I shall reserve for publication in another 
place. 
IV. Appendix. 
Since the above was written, I have had an opportunity of examining 
some fruit-bodies of Inocybe asterospora. It was observed that the cystidia 
in this species do not undergo auto-digestion, but remain fixed in the 
hymenium during the whole time of spore-discharge. In a very small 
unexpanded fruit-body the cystidia were found to be well developed, 
although only an occasional basidium had begun to produce its spores. 
The cystidia stretched only about half-way across the interlamellar spaces, 
and each one had a mucilage drop at its tip. There seemed to be no 
evidence that the cystidia acted as props to keep the gills apart, to perform 
which function their peculiar ventricose shape and excretion appear to 
render them unfitted. Since the cystidia with their mucilage drops only 
project about 0-02 mm. beyond the spores on the sterigmata, and since the 
