PSALLIOTA CAMPESTRIS 437 



is represented part of a cross-section of a living gill of a fruit- 

 body which had just expanded and had only very lately commenced 

 to shed spores. The past-generation basidia were so few in number 

 that none happened to be included in the section. In cutting the 

 section, some of the spores on the basidia nos. 1, 2, and 3 were 

 either displaced or knocked off their sterigmata, while the riper 

 spores on nos. 4 and 5 were all knocked off. The details of the 

 spores and sterigmata of these five basidia have been adjusted semi- 

 diagrammatically ; but all the other cells are shown as observed. 

 It may be remarked that nearly ripe spores are very easily detached 

 from their sterigmata by the pressure of surface tension when the 

 section to which they belong is irrigated with water ; and the 

 premature detachment of the riper spores is probably a mutilation 

 characteristic of all preparations mounted in fluids. Histologists 

 should beware of being deceived by the supposition that a 

 hymenium, after being fixed and stained and cut into sections with 

 the microtome, necessarily exhibits all the delicate morphological 

 relations which the living hymenium possesses in nature. The 

 section shown in Fig. 148, although not including any past- 

 generation basidia, includes five present-generation basidia, nos. 1, 

 2, 3, 4, and 5. These, as indicated by the degrees of pigmentation of 

 the spores, form part of a wave of development progressing from 

 the right-hand to the left-hand side of the section. Two coming- 

 generation basidia, nos. 6 and 7, have both attained about their 

 maximum protuberancy and, doubtless, are preparing for the pro- 

 duction of sterigmata. The future-generations basidia are nos. 8, 

 9, 10, 11, 12, 13, 14, 15, 16, and 17. Their free ends, which are not 

 yet protuberant, constitute the general level of the hymenium. 

 The permanently sterile elements or paraphyses are nos. 18, 19, 20, 

 21, and probably no. 22. But how, it may be asked, does one really 

 know that these elements are paraphyses ? Why should they not 

 be very young basidia which subsequently will produce spores ? 

 These questions are certainly pertinent and demand an answer. 

 Now a study of the progressive exhaustion of the hymenium 

 and of the completely exhausted hymenium proves (vide infra) 

 that a large number of elements in the hymenium never produce 

 spores but gradually enlarge in diameter, as the hymenium gets 



