MctcDougal. — Symbiotic Saprophytism. 1 1 
after attaining full size, was detached from the offshoot and 
allowed to lie on its side in damp soil. Two offshoots were 
formed laterally, and a stem-like structure from the apex. 
The corm exhibited the usual reserve material. The off- 
shoots contained quantities of starch in the cortical layers, 
and naturally in greatest quantity in the neighbourhood of 
the conducting cells. Trichomes were formed very sparingly 
on the offshoots, and on account of this fact, and also because 
the offshoots lay on the surface, the Fungus-guest had not 
gained entrance. This arrangement is of interest when the 
manner in which the Fungus is transmitted from the parent 
to the daughter-plant is considered (see p. 12). It was 
found, during a course of tests in the plant-house from 
1896 to 1898, that the plant might be forced to form a 
succession of corms and stems without leaves or flowers, in 
much the same manner as Solanum tuberosum . 
The Offshoot . The offshoot of a normal corm consists of 
a stem about 1-5 cm. long and 3 to 4 mm. thick, with two 
long or three short internodes. The nodes are sheathed by 
an encircling ragged scale composed of a single layer of cells 
and soon turning brown. The scales are from -2 to 2 mm. in 
length, and bear in their axils the naked papillae of incipient 
branches. The branches may be detected in one or two 
nodes only, and, so far as specimens have been examined, do 
not develop in the normal plant. When the parent corm 
gives rise to two young plants, it does so by separate off- 
shoots. 
The epidermis consists of a layer of cells of externally 
convex elements, the radial diameter being generally less 
than the tangential or axial. The walls are slightly and 
evenly thickened. A few dark brown hyphae may be seen 
on the surface, and the sections show an occasional pene- 
tration of the outer walls. The epidermis is separated in 
places from the layer beneath by great intercellular spaces, 
while in other portions these are entirely absent. The layer 
underlying the epidermis is not clearly differentiated as a 
hypoderm. It is composed of rounded, flattened or irregular 
