(427) 
The secondary formations in A/onotropa and Hypopitys are 
very feeble (Plate 11, Figs.6 and 7). The irregular zone 
of phloem surrounding the central cluster of vessels forms a 
few similar vessels from the elements in contact with the xy- 
lem (Plate 11, Fig. 6), but the remainder of the phloem un- 
dergoes no noticeable change. In Prerospora there is a band 
of cells lying in the inner edge of the cortex, which may be 
of the cortex, or the stele, and which undergo thickening and 
pitting (Plate 11, Figs. 8 and g), and function as mechanical 
bast: correlated with the extraordinary development of stem. 
The following statements may be made in summary of the 
foregoing: 
A complete symbiosis of very ancient origin exists between 
the Monotropaceae and the ectotropic fungi of the roots, and 
this association has been followed by very sweeping degener- 
ations in the higher plant. The fungus sheathing the roots 
of J/onotropa, has been variously determined as a Tuber- 
cinta, Sepedonium, Zygodesmus, fusidium, Epiphagos and 
Cladosporium, and that the authors found a perithecium of 
one of the Pleosporiaceae on the roots of Hypopitys. 
The fungus generally sheathes the entire root, entering the 
epidermal cells in all of the four genera discussed, forming 
masses of hyphae in the cells of Sarcodes and Ptcrospora, 
and vesicles and other enlargements in Wonotropa and Hy- 
popitys. 
The members of the family examined have lost the power of 
branching of the shoots, which are purely reproductive in their 
purpose. Vegetive propagation issecured by buds of endog- 
enous origin on the roots. Secondary roots arise exogen- 
ously in Sarcodes and Plerospora, endogenously in Ayfo- 
pitys and from the third cortical layer of the cortex in 
Monotropa. 
The root cap is least developed in Afonotropa and Hypo- 
pitys and most in Sarcodes, The histogenic layers are not 
distinguishable. The stele is much reduced. Five or six 
bundles may be recognized in Sarcodes and Plerospora, three 
or four in Hypopitys, but no distinction of this kind may be 
