20 MacDougal. — Symbiotic Saprophytism. 
roots, and failed to bring about any changes in form or 
function of fully formed offsets. In the fourth series of tests 
most beautiful and conclusive results were obtained. The 
awakened buds on old corms formed small delicate glistening 
white stems which branched repeatedly and which exhibited 
the long root-hair-like trichomes of the coralloid structures. 
From the results at hand, therefore, it seems conclusive that 
the coralloid structures are a direct adaptation whereby 
young plants may secure humous material in the event of 
the destruction of the reserve supply in the corm : or this 
adaptation may render possible the formation of young 
plants from an old corm when the previous offsets from it 
have been destroyed from any cause. This is, it is believed 
by the writer, the first successful attempt at the experimental 
formation of stem-mycorhiza. The tendency to form stem- 
mycorhiza by Aplectrum must be regarded as an individual 
variation, only called out by the deficiency of the reserve 
food-supply, since it has not been transmitted to any of 
the vegetative offspring of the plants under continuous 
observation. 
Peramium repens [Goody era repens , R. Br.). 
Peramium repens consists of a creeping stem 4 to 7 mm. 
in diameter, with internodes 4 to 5 mm. long, the leaves at 
the terminal internodes being crowded into a tuft. The 
diageotropic rhizome attains a length of 8 to 12 cm., and is 
greenish in colour due to the presence of scattered chloro- 
plasts in the cortex. The epidermal cells are rich in 
protoplasm : the outer walls are cuticularized. The cortex 
consists of twenty to thirty layers of loosely arranged ovoid 
cylindrical elements rich in starch. The fifteen to twenty 
fibrovascular bundles are arranged in an irregular circle. 
The thickish roots spring singly from the internodes and 
penetrate the substratum in both lateral and vertical directions. 
Root-hairs are abundant and persistent, and when the root 
is taken from the soil it brings away an extraordinary heavy 
coating of humus. The root-hairs are to be seen traversed 
