COPRINUS STERQUILINUS 203 



protuberant at all. The four spores of each basidium are asym- 

 metrically set upon the ends of their sterigmata, so that they stand 

 away from a line drawn through the axis of the basidium-body. 

 They therefore occupy more lateral space than the basidium-body. 

 Now all the basidia on a small area of the hymenium, such as is 

 indicated by the cross-section shown in Fig. 90, D (p. 210) or by 

 the surface view shown in Fig. 84, C (p. 199), must bear ripe or 

 nearly ripe spores at one and the same time ; for, when the upward- 

 moving zone of spore-discharge comes to envelop such an area, 

 all the spores upon it are discharged within a few minutes. Since 

 adjacent basidia must necessarily bear full-grown spores at one 

 and the same time, and since the four spores on each basidium 

 spread laterally more than do the basidium-bodies, it is evident 

 that adjacent basidia would be at a great disadvantage were their 

 bodies in contact : such contact would result in a mutual jostling 

 of the spores with the result that the development and discharge 

 of the latter would suffer serious mechanical interference. This 

 interference is obviated (1) by the introduction into the hymenium 

 of space-making agents in the form of sterile paraphyses and (2) by 

 the dimorphism of the basidia. The paraphyses surround the body 

 of each basidium so as to isolate it from the bodies of its nearest 

 neighbours. They form a continuous system of elements which 

 are welded together by their lateral walls, and they constitute 

 what may be called a hymenial pavement in which at intervals are 

 set the shafts of the basidia. The differentiation of the basidia 

 into two sets, long and short, permits of any small area of the 

 hymenium bearing, at one and the same time, more basidia — and 

 therefore more spores — than would be possible were all the basidia 

 of equal length. In order to realise this the better, let us imagine 

 that the bodies of the short basidia in the section D of Fig. 90 (p. 210) 

 were to be lengthened so that they came to be of the same length 

 as those of the long basidia. At once, some of the spores of the 

 previously short basidia would touch some of the spores of the 

 previously long basidia. The extent and frequency of the jostling 

 of the spores which would result, were the short basidia as long 

 as the long ones, will become even clearer, if we imagine the elonga- 

 tion of the bodies of the short basidia to take place in such a piece 



