ro11] CURRENT LITERATURE 473 
hemolytic effects. LorB has shown that for the mono-alcohols the same law 
holds for induced positive heliotropism and for toxic effects in Copepida and 
Daphniidae. ; 
CzAPEK describes a piece of apparatus by which one can determine quickly 
‘the surface tension of a solution. He studied the effects of alcohols (primary, 
secondary, and tertiary), esters, and urethanes upon the permeability of plant 
cells to certain solutes such as tannins and anthocyanins. Any aqueous 
solutions of these substances having a surface tension of 0.68 or 0.69 or less 
(water considered as unity) rendered the plant cells permeable to the contained 
solutes. The material studied was leaf cells of Echeveria, petiole hairs of 
Saxifraga sarmentosa, petals of Paeonia, leaf epidermis of Tradescantia, etc. 
ZAPEK believes that the surface tension of the Plasmahaut of the cells used 
is a little more than 0.68 or 0.69, and that as soon as the surface tension of the 
surrounding solution is somewhat lower, the solutes in the cell begin to pass 
out. By this means, he states, the surface tension of the Plasmahaut can be 
measured, just as osmotic pressure can be measured, by the use of the ordi- 
nary plasmolytic agents. He believes that the Plasmahaut is an emulsion of 
neutral fats. An aqueous emulsion of fats gives a surface tension of 0.68 
oro.69. Lecithin and cholasterin give lower surface tensions and are assumed 
not to play any réle in the Plasmahauten studied. 
CzAPEK emphasizes the fact that permeability is often modified by agents 
that lower the surface tension but slightly if any, as weak solutions of acids, 
chloroform, chloral hydrate, etc. This cannot be explained, of course, on the 
basis of lowered surface tension of the solution. He believes that in the case 
of acids it is due to the saponifying action of the acid on the fat of the Plasma- 
haut. : c 
On the whole, the article confirms TrAuBrE’s surface tension theory of 
Osmotic movements of solutions through plant and animal membranes. This 
theory assumes that the movement of the solutions is in the direction of the 
_ lower surface tension.—Wi11aM CROCKER. 
Alternative inheritance in elm seedlings.—There are two species of elm 
in England, Ulmus montana and U. glabra, both called “ Wych-elm,” and nu- 
merous cultivated varieties of unknown origin which are planted about English 
hedgerows and parks. Several of these latter are so distinct as to have received 
specific names, but HENRY” finds, as the result of sowing 9o different lots of 
elm seeds in 1909, that only the two species above named breed true. The 
seedlings of Ulmus glabra have a stiff, erect, unbranched stem with small 
leaves which are opposite throughout the first season’s growth; while U. 
montana has the unbranched stem drooping to one side and only its first two 
leaves opposite, the rest alternate, the leaves being larger and with longer 
petioles. All the cultivated varieties of elm tested gave mixtures of seedlings 
% Henry, AuGuSTINE, On elm-seedlings showing Mendelian results. Jour, 
Linn. Soc. Bot. 39:290-300. pls. 5. 1910.. 
