ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 475 
pedicel-cell, wliicli ultimately overtakes them ; all three eventually 
approach close to the nucleus of the pollen-tube. The growth of the 
pollen-tube is now extremely slow ; it eventually penetrates the nucellus, 
exercising a destructive influence on the cells in its immediate neigh- 
bourhood, which lose their nuclei and become filled with a brown sub- 
stance. At this period the pollen-tube sometimes branches, but ulti- 
mately only one branch is continued ; its growth being now very much 
more rapid. When the pollen-tube reaches the oosphere, not only the 
two sexual, but also the two non-sexual nuclei pass into it ; but only 
one of the male nuclei unites with the female nucleus, the other 
remaining in the protoplasm of the oosphere. 
With regard to the number of chromosomes in the gametophyte,* 
the nuclei of the prothallium or endosperm contain 8, the nuclei of 
the walls of the archegone 8, 12, or 24, and the nuclei of the oosphere 
and of the ventral canal-cell each probably 8. After the first division of 
the oosperm 16 chromosomes were found. The nuclei of the primary 
meristem of the growing-point contain 16. 
Hybridism in Cucurbitacese-t — According to experiments made by 
Mr. L. H. Pammel on a great variety of cucumbers, gourds, and pump- 
kins, fertilization takes place only within the limits of the same species, 
not with different species. Where the flowers are hermaphrodite, they 
are not self-fertile. Well-marked cases of prepotency occur in the 
order. 
Pollination of Strelitzia.J — Herr A. Wagner ascribes the peculari- 
ties of the flowers of Strelitzia reginse to its ornithophilous mode of 
pollination, it being visited largely by humming-birds. They consist 
in the union of two of the petals into a winged spear-shaped structure, 
forming a firm sheath, within which the five anthers are concealed ; and 
in the union of the pollen-grains with one another by means of cellular 
filaments. The peculiar structure of the stigma is described in detail. 
(2) Nutrition and Growth (including- Germination, and Movements of 
Fluids). 
Influence of the Chemical Intensity of Light on the Growth of 
Plants.§ — According to observations made by Prof. J. Wiesner, the rate 
of growth of the stem is, as a general rule, in inverse proportion to the 
chemical intensity of the light, attaining a maximum in absolute dark- 
ness ; while that of the leaves increases to a certain limit with the 
increase in the chemical intensity of the light, and then falls when the 
intensity is further increased. But there are exceptions to these rules. 
In evergreen trees and shrubs, the buds must be located in the periphery 
of the mass of foliage, in order to obtain sufficient light for their 
development ; while in deciduous trees they are found also in the centre 
of the foliage. The normal habit of “ sun-plants ” disappears under a 
relatively high chemical intensity of the light ; thus the leaves of Sem- 
yervivum tectorum become etiolated under these conditions. The size 
* Cf. this Journal, 1893, p. 495. 
t Bull. Iowa Agric. Exp. Stat., 1893, pp. 906-17 (1 pi. and 2 figs.). 
+ Ber. Deutscli. Bot. Gesell., xii. (1894) pp. 53-72 (1 pi. and 5 figs.). Cf. this 
Journal, 1890, p. 628, and 1891, p. 621. 
§ SB. K. Akad. Wiss. Wien, cii. (1893) pp. 291-350. 
