PANAEOLUS CAMPANULATUS 283 



transpiration. The paraphyses, in respect to their increase in cir- 

 cumference in a direction parallel to the surface of the hymenium, 

 bring an element of elasticity into the hymenium. For the basidia, 

 the order of development and exact final thickness are fixed rather 

 rigidly. The paraphyses, on the other hand, although at first all very 

 small elements, come to have a relatively wide range of size toward 

 the close of the hymenial activity. The difference in amount of 

 variation in size between paraphyses and basidia will be realised by 

 comparing in Fig. 95 (p. 281), the basidia in A with the paraphyses 

 in B. Right up to the time of the coming to maturity of the first 

 generation of basidia and often for some time after, the gills of 

 Panaeolus campanulatus are expanding in superficial area. The 

 paraphyses, during this expansion, themselves expand and thereby 

 prevent the coming into existence of spaces between themselves, 

 and between themselves and the basidia. Thus the hymenium is 

 preserved as a continuous membrane and the basidia are kept in 

 lateral contact with elements which live longer than they do and 

 which, in respect to mechanical support and supply of moisture, 

 can care for them during the whole of their existence. 



Our surface-view studies have taught us the essential facts 

 concerning the arrangement of the elements of the hymenium in 

 space and time. We are now in a position to interpret the basidia 

 and paraphyses when seen from their sides. A cross-section through 

 a gill that has been shedding spores for some time, say 24 hours, is 

 represented in Fig. 96. This illustration may be considered to 

 be an enlarged portion of the lower third of one of the long gills 

 of Fig. 85 (p. 249). However, it does not show the exact position 

 of the elements as they were actually observed in any one particular 

 preparation, but rather the generalised result of the study of a great 

 many preparations, i.e. it is semi-diagrammatic : various details 

 drawn originally with the help of the camera lucida have been brought 

 together and combined by the author so as to construct synthetically 

 an ideal section which embodies as many facts of normal structure 

 as possible. 



In Fig. 96, we can distinguish : the hymenium, hy, composed 

 of a single layer of cells which are arranged perpendicularly to the 

 plane of the gill-surface ; the subhymenium, sub, composed of two 



