ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
623 
Root-nodules of the Pea.* * * § — Herr A. Prazmowski gives a resume of 
the numerous observations on this subject by different observers, and 
details of fresh experiments of his own. He regards the structures as 
truly symbiotic, since it is only plants provided with these nodules that 
can acquire nitrogen from the free nitrogen of the atmosphere, by the 
intervention of the nodule-bacteria. The plant can derive benefit from 
the symbiosis only after it has overpowered the bacteria, the resorption 
of the products of the bacteria being the main cause of the increased 
vigour of the plant from that time. Starch is present in the nodules in 
considerable quantity, and is directly taken up by the bacteria. 
Structure of swollen Roots in certain Umbelliferse-t — According to 
M. G. de Lamarliere, the adventitious swollen roots of (Enanthe present 
a somewhat abnormal structure. The author has studied these, together 
with the swollen roots of species of Garum , Cicuta, and Sium , and found 
a series of transitions between the abnormal (Enanthe and the normal 
lateral roots of other species of the same family, and concludes by stating 
that the abnormality of (Enanthe and Garum is rather apparent than 
real. 
£. Physiology. 
Hansen’s Vegetable Physiology.:): — Dr. A. Hansen publishes a com- 
plete text-book of vegetable physiology, intended especially for the 
instruction of non-scientific readers. The subject of metabolism is 
treated in especial detail. With regard to the conduction of water, 
the author declares himself an adherent of Sachs’s theory of imbibition. 
(1) Reproduction and Germination. 
Sexual Nuclei in Plants.§ — M. L. Guignard points out that the 
number of chromatic segments in the nuclei of the embryo is exactly 
that in either the male or female nuclei respectively. There must, 
therefore, at some period in the course of development, be a reduction of 
one-half in the number of chromatic segments ; and he sets himself to 
discover at what period this reduction takes place. From observations 
made on Lilium Martagon , with which those on other plants also agree, 
M. Guignard finds that the reduction takes place suddenly, and always 
at the same stage, in both male and female organs, viz. at the moment 
of the first binary division of the pollen-mother-cell and of the embryo-sac. 
A similar phenomenon is stated by Hertwig to occur in the animal 
kingdom, in the course of development of the spermatozoa of Ascaris 
megalocephala. 
Formation of Endosperm in the Embryo-sac of Gymnosperms.|| — 
Mdlle. C. Sokolowa describes in detail the mode of formation of the 
endosperm within the embryo-sac of some Gymnosperms, especially 
Pinus, Juniperus , and Ephedra. Her observations agree, in general, with 
* Landw. Versuchs-Stat., xxxvii. pp. 161-238, and xxxviii. pp. 5-62. See 
Journ. Chem. Soc., 1891, Abstr. p. 607. Cf. this Journal, 1890, p. 59. 
f Comptes Rendus, cxii. (1891) pp. 1020-1. 
x ‘ Pflanzen-Physiologie,’ Stuttgart, 1890, 8vo, 314 pp. See Bot. Centralbl., xlvi. 
(1891) p. 196. 
§ Comptes Rendus, cxii. (1891) pp. 1074-6. Cf. this Journal, 1890, p. 358. 
|| Bull. Soc. Imp. Nat. Moscou, 1890 (1891) pp. 446-97 (3 pis. and 10 figs.). 
