1922] Essig: Morphology of Schizophyllum commune Fries 455 



apparent from their structure. It is possible that they aid in the 

 absorption of food materials, since they closely resemble haustoria in 

 shape and are found only on those hyphae which are purely vegetative. 

 Clamp connections (fig. 1, pi. 54) are found at more than half of the 

 septa in actively growing mycelium. They have been observed upon 

 the hyphae of members of the Hymenomycetes since the earliest studies 

 of their cell structure. Though they occur in a great number of fungi 

 in this group, their exact function is not understood. Harper (1902) 

 suggested that they possibly facilitated the exchange of food materials 

 between segments, but just how this is accomplished is not clear. The 

 length of the segments varies from about 30/t to more than 200jn, the 

 usual length being about SQju. The thickness of the wall varies from 

 about 0.1 to 0.5ju. In rapidly growing hyphae there are few vacuoles 

 and these are small. The protoplasm is of fine granular structure and 

 very homogeneous. As the mycelium becomes older the vacuoles 

 enlarge, oil droplets are formed, and many of the cells collapse. There 

 are two nuclei to a segment (fig. 1, pi. 54). They are small and spher- 

 ical, about 0.3 to 0.5jct in diameter. Their structure is granular. No 

 nucleoli have been seen. The nuclei are usually found about 10 to 20ju, 

 apart near the center of a segment. These compare very well with 

 the nuclei in the vegetative hyphae of Hypochnus suhtilis (Harper, 

 1902, fig. 1, pi. 1). Maire (1900) found but one nucleus in the "cells" 

 of the mycelium of Goprinus radiatus. 



The hyphae which compose a sporophore are of several different 

 types. One kind includes those which form the hairy covering of the 

 pileus and sterile surface of the hymenial plates; another makes up 

 the pileus and tramal structure, and the third forms the subhymenial 

 layer. Again, each of these types varies somewhat according to the 

 age and state of development of the sporophore. 



The hyphae which cover the pileus and sterile surfaces of the 

 hymenial plates are composed in nearly all cases of but a single seg- 

 ment, which may be as long as 3 mm. These hyphae are of a' fairly 

 uniform size and length (fig. 3, pi. 54) . They are irregularly curved 

 and tangled together. The walls are in the younger stages fairly thin, 

 but as development proceeds they gradually thicken until in very old 

 specimens the lumen has almost entirely disappeared. Two nuclei 

 are present in each hypha of the hairy covering. They are similar in 

 size and shape to those of the vegetative hyphae. They are found 

 regularly near the base of the segment. 



