1 4 MacDougaL — Symbiotic Saprophytism . 
layer is but slightly differentiated. The external layers of 
chlorophyll-bearing cells of the lower side are not so regular 
in form as those of the upper side. The air-spaces are very 
large. The median cells are almost globular in form ; 
numbers of them contain bundles of raphides. The xylem 
exhibits a strong development, and its cross-section is 
naturally greater than that of the phloem. Heavy strands of 
sclerenchyma lie externally above and below the bundles. 
The strand on the side toward an angle extends to the 
epidermis, greatly exceeding the bundle in cross-section and 
filling up the angles of the ribs appearing on both surfaces 
of the leaf. 
The heavy cuticularization of the outer surface must be 
regarded as a device for the prevention of transpiration during 
the winter-season, when the absorptive capacity of the plant is 
diminished or nullified. The dense protoplasm is fitted for 
the endurance of low temperatures, and the enormous amount 
of mechanical tissue would prevent collapse during the 
absence of turgidity. The leaves live through several months 
in which the temperature of the air is io° to 30° C., and the 
adaptations named are quite necessary for its existence. 
Spontaneous variations. Aplectrum exhibits some varia- 
tions which, if they become permanent, would change the 
entire complexion and habit of the species. 
The chief variation from the normal consists in the 
development of the lateral buds of the offshoot into coralloid 
branches, similar in general appearance and structure to the 
underground stems of Corallorhiza , which has been recently 
described by the writer ( 24 ). So far as the information of the 
writer goes, this peculiarity was first reported by H. Gilman 
in 1876. Letters of inquiry to the principal herbaria of the 
country, to dealers in native plants, including a firm near the 
original collecting ground, failed to bring further information. 
Mr. Gilman ( 10 ) writes : ‘I have lately discovered (April 9, 
1876) in the woods north-east of Detroit, Mich., two adjoining 
plants of Aplectrum hyemale , Nutt., having branched and 
toothed coral-like roots, similar to those of the genus 
