298 RESEARCHES ON FUNGI 



Coprinus picaceus is readily distinguished from all the other 

 large Coprini by having a pileus which is fuliginous- black variegated 

 with broad, unequal, superficial, separating, white scales. The sharp 

 contrast between the black pilear flesh and the large white scales is 

 reminiscent of a similar contrast in the appearance of a magpie. 

 Hence the specific name picaceus — pertaining to a magpie. 



Coprinus picaceus has the largest cystidia I have yet observed 

 in any Coprinus : they are about twice the size of those of C. atra- 

 mentarius and even exceed in length those of C. niveus. In some 

 fruit-bodies obtained at Taunton, which were half as large again 

 as the one shown in Fig. 129, the cystidia could readily be seen with 

 the naked eye interlocking the gills : they were 200-300 i^' long 

 and 50-60 ^l wide.^ In shape they were conico-cylindrical. 



The interlocking of the gills by the numerous cystidia crossing 

 the interlamellar spaces is so efficient in C. picaceus that, as in C. atra- 

 mentarius, when one divides the pileus vertically downwards into 

 two halves, the gills in the plane of cleavage split down their median 

 planes, i.e. through the trama, each gill affected leaving one half 

 of itself with one half of the pileus and the other half of itself with 

 the other half of the pileus (c/. Fig. 129, B, with Fig. Ill, p. 265). 

 In the gill-region of Fig. 129, B, the black streaks alone are hymenial 

 surfaces, while the broad grey areas are tramal surfaces. 



^ The cystidia of C. picaceus, like those of all other Coprini and of Pluteus 

 cervinus, etc., grow in length apically for some time. My measurements were made 

 on fully elongated cystidia at the time of spore-discharge. Ricken's measurements 

 {Die Bldtterpilze, Leipzig, 191.5, p. 58), namely, 100-150 /x long and 30-50 /i, wide, 

 are considerably smaller than my own. The cause of this difference is at present 

 uncertain ; possibly his cystidia had not yet grown to full length, or possibly the 

 cystidia in his fruit-bodies were considerably smaller than in mine. 



