MacDougal. — Symbiotic Saprophytism. 3 5 
a foot and a half. Oliver’s examination of Sar codes was made 
upon alcohol-material, and hence no measurements could be 
made of the penetration of the soil. Since this plant has 
a strong development of the root-system, by which it has 
a bulk much in excess of that of the shoot, it seems that 
Pterosporct has a much more reduced absorbing system than 
any saprophyte hitherto examined. 
The epidermis is coated with a dense brownish mycelium 
of a thickness equal to two or three times the radial diameter 
of the epidermal cells. The hyphae are septate and the 
mycelium is firm throughout, the hyphae which pass into 
the substratum being given off directly from the mass with 
no loosely arranged transition-layer as in Sarcodes. Numerous 
reproductive branches, resembling those of Penicillium , are to 
be seen on the external surface. A great number of sections 
were cut for the purpose, but it was impossible to identify 
these structures with the mycelium beyond doubt. It seems 
probable that they are continuous however. 
The epidermis is made up of ovoid elements with the 
narrower end between the walls of the layer beneath and 
the broader outer ends separated by a mycelial layer. The 
exfoliation of the epidermis and mycelium in the older roots 
results in leaving the outer convex and lateral walls of the 
subepidermal layer free nearly to the base or inner end. 
The hyphae penetrate the epidermal cells forming irregular 
vesicles and variously distorting the nuclei. Hyphae are seen 
to enter the subepidermal layer in some instances, though 
whether these were derived from the mycelium or not could 
not be determined. 
The root-cap of Pterospora is more than two layers in 
thickness and resembles that of Sarcodes. In free tips the 
mycelium coats the cap and penetrates the older cells, but in 
the interior of the mass of roots, where the rootlets find them- 
selves in a cid-de-sac , the mycelium penetrates the tissues 
beneath the cap. Backward along the root in all cases the 
old cells of the cap are to be seen held in the meshes of 
the mycelium. 
D % 
