1922] Essig: Morphology of Schizoph'gllum commune Fries 461 



Upon a superficial examination the "gills" appear to be much 

 branched. This is especially noticeable in dried specimens (fig. 1, 

 pi. 51). The secondary "gills" are not attached to the primary ones, 

 however, but fit in between and beneath them. Branching occurs but 

 rarely, and is the result of the anastomosing of two "gills" in the 

 early stages of development. 



2. ORIGIN AND DEVELOPMENT OF THE "GILLS" 



The origin and development of the lamellae has been studied in a 

 fairly large number of members of the Agaricaceae. In all of these 

 Atkinson (1916) recognized two general types. In the first, which 

 he called the "Agaricus" type, the hyphae form a palisade layer at 

 the roof of a well-developed annular cavity which appears on the 

 under side of the pileus; and from this palisade layer, which is the 

 hymenium primordium, the lamellae grow downward into the cavity. 

 In the second, or "Amanita" type, the gills originate as bars radiat- 

 ing out from the stipe to the under surface of the pileus. The origin 

 and development of the "lamellae" in Schizophyllum commune is 

 entirely distinct from either of the above types. The gills grow out- 

 ward from a palisade layer which forms the lining of a single apical 

 depression or cup. 



The origin of a "gill" is evidenced in cross-sections in two ways: 

 either a split appears in the palisade layer and the edges grow out- 

 ward (fig. 6, pi. 56) ; or a small area of the palisade layer becomes 

 loosened, grows outward a short distance, and then splits in the middle 

 to a point beneath the original primordial layer (fig. 9, pi. 56). In 

 both cases the growth continues in the same manner. The hyphae 

 beneath the edge of the hymenium on each side of the split grow out- 

 ward rapidly and cause the hymenial edges to turn downward, and 

 by marginal growth a pair of hymenial plates are soon formed (figs, 

 i^, pi. 57). Growth continues at the edges of these plates through- 

 out the life of the sporophore, so that in very old fruit bodies some 

 gill plates may be comparatively deep. 



BuUer (1909), noting the fact that, in cross-sections of the mature 

 specimens, the tramal layer was split to different depths, thought that 

 the "gills" arose entire and were later split due to hygroscopic ten- 

 sions. This theory had been earlier advanced by Fayod (1889), who 

 claimed that specimens grown under water have entire ' ' gills. ' ' In 

 attempting to demonstrate Fayod 's statement it was found that sporo- 

 phores grow with difficulty under water and decay after a few days. 



