1917] CURRENT LITERATURE 345 
while with Canada field peas it was saccharose, glucose, maltose. lactose. 
Timothy was found to utilize lactose when grown in darkness, but not when 
grown in light. The influence of the sugars upon the rate of respiration in the 
vetch was observed, with the result that saccharose, glucose, and maltose 
accelerate respiration very noticeably, the latter somewhat less than the other 
two. Galactose was found to be toxic to wheat, peas, corn, and vetch, even at 
low concentrations; while glucose antagonizes the toxicity of galactose, possibly 
by rendering the roots impermeable to galactose, or by altering galactose 
metabolism in such a way as to prevent formation of toxic oxidation products. 
The author suggests as a general conclusion that soluble organic substances 
produced from humus during decay may play a more important rdle in the 
organic nutrition of plants than we have hitherto thought.—CuArLEs A. SHULL. 
Osmotic pressure in parasite and host.—Using the cryoscopic method, 
Harris and LAawrENcE® have studied the osmotic relations between 7 species 
of Jamaican mistletoes and their 19 hosts. They that the sap concentra- 
tion of the chlorophyllous tissues of the parasite is nearly always higher than 
that of the mature leaves of the host, the parasites showing an average con- 
pressure. This relationship is not a nec one, however, for in several 
cases the parasites possessed sap of a lower concentration than their hosts. 
In such cases it is assumed that the host supplies more than sufficient water to 
meet its own needs, so that the parasite is not in direct competition with the 
leaves of the host, but merely secures water from the same transpiration stream. 
In cases of secondary parasitism, the osmotic pressure increases from host to 
primary and from primary to secondary parasite. The sap from the stems 
of leafless species of Dendrophthora possesses a lower concentration than that 
from leaves of species of Phoradendron and Phthirusa. The meaning of this 
is not discussed. It may involve differences in the rate of photosynthetic 
activity in the leafless and leafy forms.—CHARLES A. SHULL. 
Galls.—Essic” calls attention to the introduction of the chrysanthemum 
gall fly from Europe. This pest was not known in the United States previous 
to 1915. It causes cone-shaped galls which often distort the shoot beyond 
recognition, and eventually causes death of the infected parts. It sometimes 
destroys one-third of the crop. 
WELIs* gives us a very important study o the galls of the blackberry 
The purpose of the paper is threefold: (1) a study of the histology of the galls; 
8 Harris, J. ARTHUR, and LAWRENCE, JouN V., On the osmotic pressure of the 
Kage — of Jamaican Loranthaceae parasitic on various hosts. Amer. Jour. Bot. 
3:438-455. 1916. 
> ieee E. O., The chrysanthemum gall fly, Diarthronomyia hypogaea F. Low. 
Jour. Econ. Ent. 9:461-468. 1916. 
%* WeLts, Bertram W., The comparative morphology of the zoocecidia of Celtis 
occidentalis. Ohio Jour. Science 16:249-290. pls. 8. 1916. 
