PLUTEUS CERVINUS 109 



develop slender apices comparable with those of the basidia, and 

 their protoplasmic contents soon become reduced to a very thin 

 layer lining the wall and enclosing one large clear vacuole. They do 

 not form a compact system, but exist in the form of loosely connected 

 strings like those already described for Panaeolus campanulatus and 

 Stropharia semiglohata. 



The discharge of spores from the hymenium of two gills into an 

 interlamellar space during the spore-discharge period is illustrated 

 in Fig. 49 at E (p. 106). The arrows indicate the trajectories 

 described by some of the projectiles when shot away violently from 

 their sterigmata. Each spore is projected more or less perpendicu- 

 larly outwards from the hymenium to a distance of about • 1 mm. 

 and then, with diminishing horizontal velocity, it turns rather 

 sharply downwards, afterwards falling under the influence of gravity 

 alone with a steady terminal velocity of about • 67 mm. per second.^ 

 The spores were found to have an average length of only 5 • 95 yu- and 

 an average width of only 4-57 /i,^ and there can be no doubt that 

 they fall at the relatively slow speed of 0-67 rnm. per second owing 

 to their very small size. The gills shown at D in Fig. 47 (p. 103) are 

 about 1 cm. deep. If a spore were liberated at the top of one of 

 these gills in still air, a simple calculation shows that it would take 

 about 15 seconds to fall completely down the interlamellar space 

 before it could emerge from beneath the pileus and escape into the 

 outer air. 



When a spore of Pluleus cervinus is about to be shot away from 

 its sterigma, the usual drop of fluid is excreted at the hilum, as is 

 shown on the right of Fig. 49, E, near the letter h. A spore, when 

 shot away, is always accompanied by its drop, and two of the 

 falling spores in E are shown with drops attached. However, the 

 drops, owing to their extremely small size, evaporate very rapidly 

 indeed. Hence most of the falling spores in E are represented as no 

 longer accompanied by their drops. The spores themselves also 

 dry up very quickly and, in consequence, during their fall, become 

 boat-shaped in form. Two boat-shaped spores are to be seen in E 

 in the middle of the figure. 



Finally, we may ask : what is the function of the cystidia ? 

 ^ These Researches, vol. i, 1909, pp. 175. 2 m^^^ p. i62. 



