(422) 
or four rows of branches. A series of transverse sections of 
the apical portion of a root of Monotropa 2mm. in length 
showed five branches separated from each other by very un- 
equal angles (Plate 10, Fig. 3) ; a condition to be expected in 
such a degenerate stele and with the roots arising in the outer 
cortex. 
The secondary roots of Sarcodes are said by Oliver to arise 
exogenously, and a similar condition has been found by one 
of the authors in Prerospora (5). In Hypopztys the branches 
arise endogenously. Aouotropa presents a most interesting 
peculiarity in this regard. The initial cells of the new root 
arise in the third layer of the cortex (Plate 10, Figs. 2 and 4). 
As the embryonic tissue of the new root develops, the pressure 
set up crushes the epidermal cells of the main root first, then 
later the intervening cortical cells. This behavior is due to 
the fact that the entire root is firmly encased in the heavy 
sheathing mycelium, which possesses great tensile strength. 
This mycelial mantle is extended to cover the growth of the 
new rootlet. During the process of emergence the outer layer 
of the new root cap of the rootlet is also crushed (Plate 10, 
Fig. 2). 
The root-cap is but little developed in Hypopitys and Mon- 
otropa consisting of one to four layers, but it shows many 
layers in Sarcodes and Plerospora. In all cases the cap arises 
from a calyptrogenic layer in common with the epidermis by 
tangential division (Plate 11, Fig. 10). The outer cells of 
the cap soon become compressed and crushed by the mycelial 
mantle which completely encloses the tips in all members of 
the family we have examined. Monotropa and Hypopitys 
are reported by Oliver to exhibit a root apex free from the 
fungus; a statement that can only be accounted for by the 
supposition that this conclusion may have been based upon 
young adventitious roots which had not yet been completely 
invested by the fungus. It is possible, of course, that a root 
might outstrip the mantle during a period of rapid growth and 
become enmeshed later. 
The initial cells of the periblem and plerome lie immedi- 
