PSALLIOTA CAMPESTRIS 439 



coming to resemble the paraphyses with clear lumina which cer- 

 tainly occur in a fully exhausted hymenium. All the other cells 

 in the section are too long to be paraphyses, as will be seen by 

 comparing Figs. 148 and 152, A (p. 448). The process of elimina- 

 tion, by itself, therefore, leads to the conclusion that the elements 

 nos. 18, 19, 20, 21, and 22 are paraphyses. This conclusion is also 

 supported by comparative studies of other hymenia such as those 

 of Panaeolus campanulatus and Stropharia semiglobata, where the 

 elements are much larger and more easily differentiated from one 

 another. 



A study of Fig. 148 shows that there is no sharp and level 

 plane dividing the hymenium from the subhymenium, for the bases 

 of the hymenial elements are situated at very various levels in the 

 subhymenium. In this regard the basidium no. 4 is noteworthy, 

 for it arises at about the middle depth of the subhymenium. On 

 the other hand, basidia nos. 13 and 7 arise at a higher level, and 

 the paraphyses nos. 20 and 21 at a still higher level. The large 

 subhy menial cell which has given rise to the basidium no. 6 has 

 also produced a small subhymenial cell which acts as a pedicel 

 for the paraphysis no. 20. A similar relation appertains for the 

 basidium no. 7 and the paraphysis no. 21. The same subhymenial 

 cell no doubt often produces at least two and possibly more basidia, 

 but no good instance of this is shown in this particular illustration. 



The section shown in Fig. 149 was cut from the same mush- 

 room and at the same time as the one which has just been 

 described. The spores on basidium no. 1 were bent out of their 

 normal positions in cutting the section and have been readjusted 

 semi-diagrammatically. The other cells are all drawn as observed. 

 Here again, there are no past-generations basidia to be seen : one 

 might have been included in the section but was not. Nos. 1, 2, 

 and 3 are present-generation basidia, evidently bearing very young 

 spores, for the spores on nos. 2 and 3 are only partly grown, while 

 those on no. 1, although of full size, are as yet unpigmented. Nos. 

 4, 5, and 6 are coming-generation basidia, a fact indicated by their 

 protuberancy which is greatest in no. 6. Basidia nos. 1, 2, 3, and 

 6 appear to form part of a wave of development which is passing 

 across the section from left to right. Nos. 7, 8, 9, 10, 11, and 12 



