NAKED-SPORED FUNGI— BASIDIOMYCETES 121 



stitutes what are popularly termed the gills. The whole of 

 this surface is covered with a layer of elongated cells, packed 

 closely side by side, and attached at the base. These hymenial 

 cells are of three kinds intermixed, although regarded by some 

 authors as only variations or modifications of one type 

 (Fig. 47). The most important of these cells are the fertile 

 ones, or those which bear the spores at the apex, and in fact 

 are the true basidia. We may assume it to be generally true 

 that these basidia are more or less of a clavate, or club-shaped, 

 form, narrowed a little at the base into the supporting hypha, and 

 obtuse at the apex, where they are crowned with four delicate, 

 short, spine-like processes — the sterigmata, each of which is 

 ultimately surmounted by a spore. Thus, then, each basidium 

 is normally tetrasporous, producing at its apex four spores. 

 In rare cases there may be only two, but typically there are 

 four. The cell of the basidium, as indeed all the cells of the 

 hymenium in the Agarics, is uncoloured, but the spores may 

 be either colourless or coloured according to the group to 

 which the species belongs. The second kind of cells to be 

 observed on the hymenium are often larger and longer than 

 the basidia, naked at the apex — that is to say, without sterig- 

 mata or spores. They also are much fewer in number, and are 

 called cystidia. In some genera these cystidia are very large 

 and conspicuous, and in certain Polyporei and Thel&phorei they 

 undergo considerable modification, and are sometimes coloured. 

 At least such are the features of the processes which hold an 

 analogous position to the cystidia, and which are now generally 

 regarded as modified cystidia. As to the functions of these 

 cells opinion is still divided. Some have claimed for them the 

 character and functions of antheridia, but the majority follow 

 De Seynes in regarding them as hypertrophied basidia, and 

 possibly their mechanical function is that of keeping the 

 lamellae apart. The third kind of cells on the hymenium are 

 rather smaller than the basidia, similar in form, rounded at the 

 apex, but without sterigmata, and are sometimes called para- 

 physes. There can be no doubt that they are abortive basidia or, 

 as De Seynes terms them, "atrophied basidia." So that the 

 three kinds of cells on the hymenium are but three forms or 

 conditions of the same organ — the true basidia, the hyper- 



