ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
707 
opposing tendencies, one tending to tlic increase, tlic other to the de- 
crease of the number of leaves in a whorl. 
Root-tubercles of Leguminosae.* — Mr. H. L. Bolley enumerates 
21 species of Papilionaceae, natives of northern Dacotah, growing in a 
great variety of situations, which produce tubercles on their roots. 
Though he has not positively determined the point, the author inclines 
to the opinion that each host has its specific tubercle-producer. 
Root-tubercles of Arachis.t — M. Ii. Lecomte describes the structure 
of the root-tubercles of Aracliis ltypogea , which agrees closely with that 
of those found on the stem of Trifolium repens. The central paren- 
chyme contains protoplasmic bacteroids and mycelial filaments passing 
from cell to cell. The formation of the tubercles is accompanied by a 
very large deposit of nitrogen in the seeds in the form of aleurone. 
M. Lecomte points out the very great importance in agriculture of this 
property of Arachis of accumulating nitrogen out of the atmosphere. 
Root-hairs. :J — According to Mr. T. Jamieson, in many plants the 
root-hairs are not composed of closed cells, but are furnished with a 
small aperture a little below the apex, through which even solid particles 
can be taken up by the hair out of the soil. The aperture was observed 
in the following plants : the turnip, pea, carrot, lupin, tobacco, barley, 
and potato. 
B. Physiology. 
(1) Reproduction and Embryology. 
Embryology of the Amentiferae. — MissM. Benson § has investigated 
the embryology of various species belonging to the Cupnliferae, Cory- 
laceae, and Betulaceae. They agree in the hypodermal character of the 
archespore, and in the presence of tapetal cells; the archesporial cells 
are arranged in strands, forming a sporogenous tissue. In all of them 
the pollen-tube sometimes branches, and forms recurved caeca before 
entering the nucellus. There is also a prevalent formation of caeca by 
the embryo-sac. 
The Cupuliferae ( Fagus , Castanea, Quercus') show but little departure 
from the ordinary type of Angiosperms ; but in Castanea there is a 
remarkable formation of tracheids at the base of the embryo-sac. 
The Betulaceae ( Betula , Alnus ) agree with the Casuarineae in their 
chalazogamic character, i. e. the pollen-tube does not enter the micropyle, 
but penetrates the nucellus from the chalazal region ; and this is also 
the case with the Corylaceae ( Corylus , Carpinus). In the two latter 
genera there are a large number of megaspores, which continue their 
development up to the stage of forming two or four nuclei. 
In all the Amentiferae the pollen -tube goes through a resting period 
varying from one month in Betula to eleven months in some species of 
Quercus , no trace of the ovule being present, in the latter case, at the 
time of pollination. In the chalazogamic orders Corylaceae and Betu- 
laceae, the course of the pollen-tube very closely follows that described 
* Agric. Sci., vii. (1893) pp. 58-66. See Bot. Centralbl., 1894, Beih. p. 294. 
f Comptes Rendus, cxix. (1894) pp. 302-4. Cf. this Journal, ante , p. 83. 
t Science (New York), xxii. (1893) pp. 354-6 (44 figs.). See Bot. Centralbl., 
1894, Beih., p. 229. § Trans. Linn. Soc. (Bot.), iii. (1894) pp. 409-24 (6 pis.). 
