68 RESEARCHES ON FUNGI 



do not always succeed in obtaining a suitable orientation for securing 

 the discharge of all their spores. One often notices that one side of 

 a gill is powdered with fallen spores whilst the other is not. The 

 powdering is due to the misplacement of the gill : the powdered side 

 has looked slightly upwards, and has therefore caught a large 

 number of spores which have fallen vertically after being shot away 

 from the hymenium. Such misplacement of a gill may be brought 

 about by various causes, such as the displacement of the pileus 

 owing to the action of the wind on the fruit-body as a whole, the 

 partial drying of the free edges of the very delicate gills, etc. If 

 the gills were not so acutely wedge-shaped and weakly constructed, 

 doubtless powdering would occur less often. It is interesting to 

 note that similar powdering occurs upon the gills of Coprinus 

 plicatilis, which in general form resembles Bolhitius flavidus. 



The Hymenium. — In face view, the hymenium exhibits not a 

 trace of the mottling which is so characteristic of the Panaeolus 

 Sub- type ; but instead, on every small area of the gill-surface, 

 basidia are to be found bearing spores in various stages of develop- 

 ment. The appearance of the spores on one small area is shown in 

 Fig. 33 at B. This drawing, which may be contrasted with similar 

 drawings for Panaeolus campanulatus given in Volume II (pp. 257, 

 258), shows not only the absence of mottling but also that basidia 

 which bear spores of about the same age are well separated from one 

 another. All the elements of the hymenium, including the spores 

 of B, are shown at A which represents a stage of hymenial develop- 

 ment just previous to the beginning of spore-discharge. Here, it 

 will be observed, the basidia appear to be developing in no very 

 regular manner. One cannot speak of a definite first, second, or 

 third generation of basidia, etc., for the basidial population shows all 

 gradations of age on one small area. However, one rule for spore- 

 production is generally kept, and that is that adjacent basidia shall 

 not produce spores at one and the same time. This ensures mutual 

 mechanical non-interference between the spores of neighbouring 

 basidia. 



The elements of the hymenium, as a rule, are two only — basidia 

 and paraphyses. Cheilocystidia occur along the free edge of each 

 gill, but only very rarely have I seen an occasional pleurocystidium 



