1905] CURRENT LITERATURE 469 
in darker green, thicker foliage, with increased starch production and decreased 
transpiration; second, direct toxic action on the foliage and fruits. The whole 
question, on which many conflicting views have been published, has been critically 
examined by SCHANDER.'® Many writers have attributed the stimulating action 
of Bordeaux mixture to the entrance of small quantities of copper into the plant, 
both through the cuticle and through the stomata. SCHANDER finds that leaves 
injected with a solution of CuSO,, 1 part in 10,000,000, and allowed to lie in the 
solution 24 hours, showed poisonous effects, while much more concentrated 
solutions were unable to penetrate the uninjured epidermis when applied exter- 
nally. The argument is that the cuticle_prevents the penetration of very dilute 
solutions of copper, such as might result from solution of the particles of copper 
fompounds applied to the leaf, but if any copper enters the cells the results are 
injurious, never stimulating. By growing plants in water cultures with dilute 
Solutions of copper, it was found that the young roots were gradually killed, 
whereupon another crop of roots was formed, which also was finally killed, etc. 
Here again there was no stimulating action, although the top of the plant remained 
uninjured, showing that the copper was accumulated by the root cells, even from 
Very dilute solutions, but was not passed on into the vascular system. In soils, 
4 more concentrated solution of copper was required to produce toxic effects on 
account of their absorption. By appropriate experiments it is also shown that 
neither the lime compounds nor the traces of iron produce stimulating effects. 
_ The true explanation of the phenomena is found in the physical action of 
the coating itself. ‘The same results were produced by shading plants with glass 
!0 which a spray of Bordeaux mixture had been applied, also by the use of thin 
% per or dust. Good results were obtained only in bright sunny weather, = 
injury resulted during cold rainy seasons. This, no doubt, explains ae ee 
cting reports of various investigators. The toxic effect of the mixture 1s found 
to be due to solution of the copper, caused by the secretions of glandular hairs 
aS in the peach, phaseolus, and sunflower.—H. HASSELBRING. 
THE FINAL sections of Davis's Studies on the plant cell” have appeared. Sec- 
tion IV deals with cell unions and nuclear fusions. The subject is treated under 
thtee heads: (1) protoplasmic connections between cells, (2) sexual cell unions 
and nuclear fusions, and (3) asexual cell unions and nuclear fusions. ce _ 
Says, “The test of a sexual act must lie with the history of the elements wie ae 
If they are shown by their morphology and developmental history to be sexu 
cells or gametes, then their fusion becomes @ sexua process." ogre qed 
and nuclear fusions are treated under three heads: (1 cell Ee ee 6 
‘apparently no sexual relations, (2) cell fusions which are substitutes em es 
“cestral sexual process now suppressed, and () extraordinary mom" 
; Pane b ith 4 
*6 ScHaNDER, R., Ueber die physiologische Wirkung der Kupfervitriolkalkbrihe 
Landy. Jahrb. 33:517-584. 1904. 
7 Davis, B. M., Studies on the plant cell. 
‘seaen Naturalist 39:217-268, 449- 
499, 555-599, 695-740. 1905. 
