ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
311 
injurious than chlorides ; sulphates less injurious than either. Salts of 
barium and strontium are less prejudicial than those of calcium. Potas- 
sium chromate and bichromate, cupric sulphate, and ferric sulphate, are 
especially poisonous. 
Light appears to have no influence on the germination of seeds. 
Influence of Light on Dorsiventral Organs.* * * § — From observations 
made by Miss K. C. Burnett on leaves of Salix alba , it appears that when 
palisade tissue has once been formed on the surface of a leaf exposed to 
light, it cannot be changed, but that the parenchymatous tissue of the 
under surface, if exposed for a sufficiently long time to the action of 
light, will take on the characteristics of palisade tissue. Gemmae of 
Lunularia will develop rhizoids on the morphologically upper surface 
when placed in contact with the soil, but only when the gemma is in a 
very young stage of development. 
Assimilatory Inhibition.j* — From a further series of observations 
made on a variety of plants, Dr. A. J. Ewart states that chloroplastids 
developed in darkness, whether they become green or are etiolated, may 
possess a fairly active power of assimilation corresponding to their size 
and depth of colour. The power of assimilation is absent whilst the 
etiolated leaf is quite young, and finally disappears again after the leaf 
has been kept for a long time in darkness. Etiolated leaves exposed to 
light in an atmosphere entirely deprived of C0 2 turn green, and may 
acquire an active power of assimilation, which, however, soon begins to 
weaken, and is in most cases rapidly lost. From experiments on CJiara 
he finds that cells from which nearly all the chloroplastids had escaped 
could nevertheless still remain living, though incapable of regenerating 
fresh chlorophyll, for a period of a year. 
Biology of Woody Plants.J — Herr K. Reiche has investigated the 
structure and physiology of the wood of many plants belonging to 
widely separated natural orders, natives of Chile. He finds that the 
evergreen and the deciduous condition pass into one another by insensible 
gradations. They can, however, be classified into those which display an. 
uninterrupted increase in thickness, and those in which the increase in^ 
thickness is periodically interrupted by periods of repose. The activity 
which brings about the increase in thickness precedes the unfolding of the 
leaves. When first formed, the new tissue is free from starch, while it' 
is found abundantly up to the close of the previous period of growth. 
Regeneration of Split Roots. § — As the result of experiments on 
plants belonging to widely separated natural orders — Zea Mays , Vicia 
Faba , Philodendron robustum, &c. — Herr G. Lopriore states that the 
regeneration of split roots always takes place by apical growth, the exact 
process being greatly dependent on the mode in which the section has 
been made. Regeneration may take place in all the tissues, — epiderm, 
cortex, and vascular system. A healing-tissue is formed in the inter- 
* Bull. Torrey Bot. Club, xxiv. (1897) pp. 116-21 (1 pi.). 
t Journ. Linn. Soc. (Bot.), xxxi. (1897) pp. 554-76. Cf. this Journal, 1896, 
p. 649. % Jakrb. f. wiss. Bot. (Pfeffer u. Strasburger), xxx. (1897) pp. 81-115. 
§ Abhandl. K. Leopold.-Carol. Deutsch. Akad. Naturforscher, lxvi. (1896) 
pp. 209-86 (8 pis.). 
