242 RESEARCHES ON FUNGI 



of the basidia and paraphyses, whilst those of Type II are 

 based chiefly on the structure and arrangement of the basidia 

 and cystidia, and upon the mode of expansion of the pileus. Each 

 Sub-type is more or less different from the other Sub-types in the 

 organisation of its fruit-body as a whole for the successful pro- 

 duction and liberation of the spores. The exact nature of the 

 Sub -types will be best realised when they are described in con- 

 nection with specific fungi included in them. These descriptions 

 will therefore not be given in this place but in succeeding Chapters 

 in this volume and the next. 



Order of Description of the Sub-types. The Sub-types of 

 Type I, already given on a previous page, are supposed to be 

 arranged in order of increasing complexity ; but this order will 

 not be kept in the following Chapters. I have thought it best 

 to describe Sub-type D, the Panaeolus Sub-type, first. This has 

 been done because it is a very common clear-cut Sub-type and 

 has been investigated by me in great detail. When the reader has 

 read the description of this Sub -type, he will have but little diffi- 

 culty in understanding the other Sub-types of Type I, although 

 some of them will be dealt with much less fully. 



Order of Investigations. Having realised that, in the 

 Agaricineae, the successive development of the basidia, which 

 results in the discharge of a continuous stream of spores often 

 for many days, is a striking phenomenon calling for detailed 

 investigation, I determined to make a careful study of the hymenium 

 of the Common Mushroom (Psalliota campestris). After the work 

 upon this species was begun, a number of points were elucidated 

 including the fate of the exhausted basidia. By examining very 

 thin surface sections of the gills without immersing them in water, 

 it was found that basidia which have discharged their spores can 

 be recognised by the remains of their sterigmata, for these persist 

 in the form of tiny stumps. However, the difficulty of finding 

 out whether or not the hymenium contains paraphyses special 

 sterile elements soon came to the fore. Then, having observed 

 that the hymenial elements of the Mushroom are very small 

 compared with those of many other Agaricineae, I came to the 

 conclusion that the Mushroom was not a good starting-point for 



