ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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causes frequently tetramery or pentamery of the flowers, lobing of the 
margin of the petals, and a change in the venation of the sepals. The 
author traces a close similarity between these phenomena and those of 
the castration of animals caused by parasites. 
Cause of the Direction of Growth of Pollen-tubes.^ — According to 
experiments made by Dr. H. Molisch, the direction of the growth of 
pollen-tubes is chiefly regulated by two causes — by oxygen, they being 
negatively aerotropic, and by the stigmatic secretion. 
Physiological Researches on the Germination of Seeds.f — M. E. 
Heckel describes various experiments made to ascertain the action of 
certain chemicals on the germination of seeds. The results may be 
summarized as follows : — (1) Contrary to the statements of Detmer, 
flower-of-sulphur does not accelerate the germination of even those 
seeds which contain sulphur as one of their constituent elements ; 
(2) Sulphurous acid suspends or arrests germination according to the 
species of plant with which it is brought in contact ; (3) Sulphuric acid in 
weak solution does not arrest germination ; when, however, the percentage 
reaches 0*2 the germinative process is arrested. Solutions of various 
salts were tried ; salicylate of soda was found, even in small doses, not 
only to suspend the germination of seeds (Fagopyrum esculentum, Solanum 
nigrum, Brassica Napus) but also of tubers (Helianthus tuberosus); 
(4) Desiccation of seeds between 40^ and 60° C. does not accelerate 
germination, but permits young plants to develope more rapidly ; 
(5) High humid temperatures of from 40° to 60° considerably accelerate 
germination. 
(2) Nutrition and Growth (including* Movements of Fluids). 
Fixation of Nitrogen by Leguminos8e.| — M. E. Breal has already 
shown that it is possible to cause nodosities to arise on the roots of 
LeguminossB by inoculating them with bacteria. He now gives a 
resume of certain cultures of Legiiminosee which he has carried on for 
the last two years, and he agrees with MM. Hellriegel and Willfarth and 
M. Berthelot, when they state that these plants can grow in a soil which 
is very poor in nitrogen. By means of their roots they furnish and fix 
this element in the soil which bears them, and well merit the name of 
“ ameliorating plants,” which has for some time been given to them. 
Absorption of Nitrogen by Plants from the Soil.§— M. A. Muntz 
has determined, as the result of a series of experiments, that, eoutrary 
to the view generally entertained, the higher plants, such as cereals and 
beans, can absorb nitrogen directly from the soil when presented to 
them in the form of a salt of ammonia; and that consequently the 
nitrification of ammoniacal manures is not an essential condition to 
their utilization. 
Relation between the Physical Characters of Plants and the 
Richness of the Soil-H — M. S. Ville describes various experiments made 
* SB. K. K. Zool. Bot. Gesell. Wien, xxxix. (1889) p. 52. 
t Jouru. de Bot. (Morot), iii. (1889) pp. 288-94, 297-305, 315-9, 332-5. 
X Comptes Rendus, cix. (1889) pp. 670-3. Cf. this Journal, 1889, p. 781. 
§ Comptes Rendus, cix. (1889) pp. 646-8. 1| T. c., pp. 628-31 
1890. P 
