ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
499 
odour is, as a rule, increased by heat and light. With Nicotiana longi - 
flora the flowers are open and fragrant only at night ; and here the dark- 
ening of the whole plant for three or four weeks is necessary to destroy 
the scent. Nycterinia capensis is peculiar in the fact that the odour is 
apparently dependent on the presence of starch in the parenchyme of the 
petals. 
Relationship between Plants and Snails."' — Herr F, Ludwig gives 
a resume of malacophilous plants, i. e. those that are fertilized by the 
agency of snails and slugs. He further describes the various modes in 
which plants are protected against the attacks of molluscs, especially by 
the presence in the cell-sap of raphides and of tannin. There can be no 
doubt that galls are a protection against the ravages of these and of other 
animals. Many spores and other germs do not lose their power of 
germination by passing through the intestinal canal of snails ; and these 
animals probably play a considerable part in the dissemination of 
fungi. 
Constitution and Formation of Peat.f — According to Dr. J. Friih, 
peat may be formed either above the surface of the water, when it is 
composed chiefly of remains of Sphagnum , Eriophorum, and Calluna , the 
latter being replaced in the West of Europe by Erica tetralix, or below 
the surface, when it consists chiefly of Hypnum , Carices, and grasses. 
But almost any plant except fungi and diatoms is capable of contributing 
to the formation of peat. The chief chemical characteristic of peat is the 
presence of large quantities of humic and ulmic acids, the latter very 
commonly in combination with lime, and forming the substance known as 
dopplerite. 
B. CRYPTOGAMIA. 
Cryptogamia Vascularia. 
Tmesipteris.J — M. P. Dangeard describes in detail the five species 
which, according to him, constitute the genus Tmesipteris, three of 
which are new — T. Vieillardii, T. elongatum, and T. lanceolatum. The 
following are some of the more important general characters of the 
genus : — 
All the species are rootless, the function of the root being performed 
by a rhizome covered with absorbing hairs. Most of the species grow 
on tree-ferns, but T. Vieillardii is found on moist soil. The walls of 
the cortical cells often become converted into mucilage, the cell-cavities 
being filled by a black substance. In the stem the tracheids which form 
the protoxylem occupy the centre of the vascular bundles, but are often 
replaced at an early period by a lacuna ; these are surrounded by the 
protophloem. The centre of the stem is in some species occupied by 
a pith, which may be parenchymatous or collenchymatous, or may be 
occupied by fibrous cells. The sporange has the form of a two-chambered 
egg, and is situated on the upper part of a petiole ; the author regards 
the sporangial leaf as the result of the fusion of two leaves. The cortical 
* Bot. Centralbl., 1891, Beili. 1, pp. 35-9. Cf. this Journal, 1890, p. 486. 
t Ber. Schweiz. Bot. Gesell., 1891, pp. 62-79. 
X Le Botuniste (Dangeard), ii. (1891) pp. 163-222 (7 pis.). 
