MacDougal. — Symbiotic Saprophytism. y 
offshoots, 2-4 cm. in length and composed of three or four 
internodes, are given off from the upper internode of the 
corm, and from their extremities arise new plants. The 
fourth or fifth internode becomes apogeotropic, turns upward 
and begins to swell, forming a new corm. About twelve to 
twenty unbranched roots are given off from the lower inter- 
node of the corm, attaining a length of 5-10 cm. The 
reserve material in the parent corm is drawn upon so slowly 
by the offspring that its contents are not exhausted until one 
or even three seasons have passed. In consequence of this 
fact plants may be found with two or three corms of different 
ages attached by the old offshoots. 
The Roots. The roots are furnished with persistent root- 
hairs from the base to within 2 mm. of the apex, which bears 
a distinct root-cap. Thickly intermeshed with the hairs were 
great numbers of brown filaments derived from the mycorhizal 
strands of Oak, Maple, or other neighbouring trees. In several 
instances a mycorhiza of a tree was found applied to the side 
of roots from the base to a point near the apex so closely as 
to be incapable of separation, except by tearing the superficial 
layers of the root. Separate hyphae from the tree- mycorhiza 
were given off laterally and entered the epidermal layers as 
described below. It is thus to be seen that Aplectrum, the 
Fungus, and Oak or Maple trees form a nutritive union. It 
is difficult to estimate the symbiotic balance existing among 
the three members. The Fungus forms a complete coating 
on the roots of the tree, but covers only patches and strips 
on the Aplectrum. The presence of an endotropic mycorhiza 
in the roots of the Aplectrum would lessen the tendency to the 
formation of an ectotropic layer with a second Fungus. It 
seems reasonable to suppose therefore that the interchange 
between the tree and the Fungus is much greater than 
between the Fungus and Aplectrum. That the other two 
are parasitic upon the Aplectrum is rendered improbable by 
the fact that the largest and most robust specimens collected 
and received from elsewhere were abundantly covered with 
the ectotropic Fungus. The Fungus must therefore be 
