66 SUMMARY OF CURRENT RESEARCHES RELATING TO 
the anatomical study of the leaf is of great importance for the determi- 
nation of the genus and the species, the more so in consequence of the 
rarity of the flowers and of the fruits. 
Leaves of Aloinese.* * * § — Sig. D. Lanza describes the structure of the 
leaves in a large number of Aloinese, which agree in all essential 
characters. The cuticle varies greatly in thickness according to the 
species ; the epiderm is homogeneous, and is composed of a single layer 
of cells ; next to the epiderm comes an assimilating tissue, consisting of 
a very variable number of cells. Scattered through the assimilating 
parenchyme are a number of cells with suberized walls and sometimes 
of great length, containing raphides. The vascular bundles are of 
uniform structure throughout the order, and each is surrounded by its 
own endoderm ; the cells which contain the peculiar bitter principle 
constitute a layer outside the sieve-cells. The surface of the leaves of 
Haicorthia and Gasteria is covered with excrescences originating from 
below the epiderm, and composed of colourless cells, the function of 
which appears to be to protect the plant from excessive insolation. 
The author states that the leaves of Haicorthia fasciata altogether 
change their habit with the locality in which they grow, being flat or 
erect, according as they are exposed to shade or to sunlight. He finds 
no sufficient characters, either in the flower, the fruit, or the leaves, for 
distinguishing the genera Aloe , Gasteria , Haicorthia , and Apicra. 
Filaments in the Scales of the Rhizome of Lathraea squamaria.*— 
Herr A. Schenfel maintains his previous view that these structures are 
not of a waxy nature, but are living bacteria, of which he finds also the 
zoogloea-form. This view he supports by microchemical evidence 
against the adverse criticism of Jost. Their presence, or at all events 
their abundance, appears to depend on the richness in protoplasm of the 
scales or glands in connection with which they are found. 
Trichomes of Corokia budleoides.+ — Hr. A. Weiss describes the 
structure and the mode of development from a single epidermal cell of 
the remarkable hairs which cover both surfaces of young, but the under 
surface only of mature leaves, as well as the axis of this plant (Comaceae). 
They are of the form which he designates T-hairs, consisting of a very 
elongated cell fixed transversely at nearly its centre to a pedicel com- 
posed of four or five short cells. The membrane of the T-cell is largely 
impregnated with calcium carbonate ; and the hairs evidently serve the 
purpose of protecting the plant against the attacks of animals, and also 
against the penetration of the mycele of fungi. 
Bulbils of Malaxis.§ — According to Herr Y. A. Poulsen, the bulbils 
often found on the apices of the leaves of Halaxis palwlosa resemble 
ovules in having their axis clothed with an integument-like sheath. 
They have neither vascular bundle nor root, and are developed from the 
epiderm of the mother-leaf. New bulbils are sometimes formed at the 
margin of the sheath. 
* Malpighia, iv. (1890) pp. 145-67 (1 pi.). 
t Bot. Ztg., xlviii. (1890) pp. 417-30 (1 fig.). Cf. this Journal, 1889, p. 89. 
j SB. K. Akad. Wiss. Wien, xcix. (1890) pp. 268-82 (1 pi. and 1 fi?.). 
§ ‘ Ora Bulbildannelsen hos Malaxia paludosa,’ Kjobenham, 1890. See Bot. 
Centralbl., xliii (1890) p. 336. 
