ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 
215 
Aerial Roots of Orchidese.* * * § — Herr E. Falla describes the structure 
of the aerial roots in two species of Orchideie, Angrsecum ornithorliyn- 
chum and Pohyrliiza sp. 
In the former species the velamen is furnished with multicellular 
conical papillce, having thickened walls, between which the velamen often 
consists of only a single layer of cells, thus greatly increasing the 
absorbing surface of these roots, which also serve as the assimilating 
organ. The leaves are very small and narrow, and of simple structure, 
only three vascular bundles passing into them. 
In Polyrliiza the aerial roots have generally a triangular section, 
the velamen being well developed on the side in contact with the sub- 
stratum, consisting there of several layers of cells, while it is more or 
less entirely suppressed on the two other sides. The velamen is 
furnished with hairs, which apparently serve both as absorbing organs 
and as organs of attachment. 
/3. Physiology. 
(1) Reproduction and Germination. 
Anatomical Characters of Hybrids. M. M. Brandza has examined 
the anatomical structure of the following hybrids, viz . : — Rosd rugosa- 
fimbriata , Cornus tricolor ( C . alba- f- G. mas), Cirsium arvense-lanceolatum, 
Marrubium Vaillantii (M. mlgare-\-Leonurus cardiaca), Medicago falcato- 
sativa, and Sorbus Jiybrida ( S . Aucujparia + S. Aria ) ; and, while the 
characters are in each case constant, he finds the following remarkable 
differences between them. In (1) none of the characters of the hybrid 
are intermediate between those of the parents, but some of the charac- 
ters are those of one parent, while others are those of the other parent. 
In (2) the stem, petiole, and principal veins of the leaf are intermediate 
in character between those of the parents, while the lamina presents 
some of the characters of each parent side by side. In (3) the stem 
and floral axis exhibit intermediate characters, while the petiole has 
some characters of each parent unchanged. In (4), as in (I), there is 
no blending of characters, but some of those of each parent are 
presented side by side. In (5) and (6) the structure is intermediate. 
Proterandry and Proterogyny.J — According to observations made 
by Mr. T. Meehan, the proterandry or proterogyny of a species is a point 
frequently governed by the conditions in which it grows. Thus, in 
the case of the hazel, while in this country the male and female flowers 
mature nearly simultaneously, in America, with sudden high tempera- 
ture, the male flowers will open long before the female flowers, while with 
long-continued temperate heat, the female flowers will advance more 
rapidly than the male. 
Flowers and Insects.§ — Continuing his observations on the mode of 
fertilization and the fertilizers of American plants, Mr. C. Robertson 
* SB. K. Akad. Wiss. Wien, xcviii. (1889) pp. 200-7 (2 pis.), 
f Rev. Gen. de Bot. (Bonnier), ii. (1890) pp. 433-45, 471-9 (39 figs.). 
x Proc. Acad. Nat. Sci. Philad., 1890, pp. 268-70. 
§ Bot. Gazette, xv. (1890) pp. 199-204. Cf. this Journal, 1890, p. 628. 
