 qo10] CURRENT LITERATURE 389 
cultural experiments and because of the detailed morphological and anatomical 
features of both symbionts. The fungus causes the conversion of starch into 
_ sugar by its diastase. Its function results from its enzymatic quality, which, 
with the solution of carbohydrates in the plant cell, induces the development 
of the seed, not by bringing soluble materials to the cell, but by transforming 
_ substances already there. BurGEFF suggests here the unproven fact of diffu- 
a sion of the diastatic enzyme out of the fungal hypha through the Plasmahaut 
On the whole, the relations between the plant and the mineral salts of the 
soil are of striking importance for the origin and maintenance of the orchid 
symbiosis. Although the structures show a gain in nitrogenous substances, 
the habitats of orchids, and cultural experiments exclude the possibility of free 
N-absorption. No anatomical features can prove the absorption of organic 
Bsivdraces: although diastase and emulsin are common to all fungi, material 
for the action of the former is lacking in the soil, and we are in ignorance con- 
cerning the substance in the soil digested by the latter. Any substance taken 
up by the plant, either through its roots or by means of the fungus, must first 
be made soluble by the fungus itself, or by its exoenzymes in the substratum.— 
Grace L. Crapp. 
MINOR NOTICES 
Farm weeds.—The preparation of a scientific manual for the use of the 
ordinary layman is admittedly a difficult task, but it has been successfully 
_&ccomplished by CLARK and FLETCHER,? whose volume upon farm weeds is the 
best that has yet appeared upon this subject. The remarkable simplicity 
Without the sacrifice of scientific accurracy is due largely to the splendid 
ability of the late Dr. James FLETCHER, who thus adds one of the latest of his 
Many valuable contributions to botany and — More than 200 of 
: eeds of Ca 
The most valuable aid to the recognition of different species is a series 
of 76 full-page plates, colored with the greatest accuracy. T hey include 
Lee arpa 
__ ?Ctark, Grorce H., and FLETCHER, JAMES, Farm weeds of — Second 
ition. 8vo. pp. 192. pls. 76. Ottawa: Department of Agriculture, Dominion of 
1909. $1.00 (single copies only, for sale by meat of Stationery, 
Government Printing Bureau, Ottawa). 
