402 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
internal lacuna. Tlie increase, either in diameter or in thickness, of 
certain elements near the haustoria, and a considerable increase in the 
size of the nuclei. The large size and the nature of the sieve-tubes, 
which vary in form, and which recall the general type in woody plants. 
The large size and the number of the laticiferous tubes, which are very 
distinct from the pericyclic fibres. 
Structure of Piperaceae.* * * § — M. A. de Candolle calls attention to 
several interesting points connected with the structure of the stem of 
climbing plants belonging to the Piperaceae, especially to the large size 
of the vessels compared to those of allied species which are not 
climbers. 
Polystely in Primula. f — Mr. D. T. G wynne Vaughan finds remark- 
able variations in structure as to polystely within the same species in 
the genus Primula , even in different regions of one and the same plant. 
In P. japonica, obtusifolia, denliculata , and involucrata , the normal stem- 
structure of 2-4 anastomosing steles is by no means universal ; all the 
steles are very often defective or imperfect. In P. japonica and denti- 
culata certain structures were invariably found in the petiole which are 
similar in all essential respects to normal and perfect steles. 
Lenticels of Monocotyledons.^ — Herr A. Weisse describes the oc- 
currence of true lenticels in a variety of plants belonging to different 
orders of Monocotyledons : — in the aerial roots of Aroideae ( Monstera 
deliciosa , Philodendron , Anthurium) ; in arborescent Liliaceae ( Aloe, 
Bracsena, Cordyline) ; and in the rhizome of Iris germanica . In the 
Pandanaceae and Palmae, on the other hand, no true lenticels could be 
detected, either in the stem or in the root. Neither is any true periderm- 
found in these plants. In the aerophilous roots of the Pandanaceae, the 
peculiar pneumathodes assume the function of lenticels. 
Resinocysts.§ — Herr M. Schoennett describes under this name bodies 
of a very peculiar nature found in the stem, leaf-stalk, and lamina of a 
species of Begonia . They are usually hemispherical structures, in close 
apposition to the cell-wall, always in pairs, one on each side of the wall. 
They have a characteristic stellate appearance. They are always found 
in the fundamental parenchyme, in immediate proximity to the primary 
vascular-bundle system. They vary in breadth between 8 and 12 /a, 
and in length between 12 and 20 /x. They are attached to the cell- 
wall by a very short stalk. With regard to their chemical constitution, 
they are undoubtedly of a resin-acid nature. They are completely solu- 
ble in alcohol, and take up stains very readily. Other chemical reactions 
are given in detail. The stalk consists of pure cellulose. As regards 
their function, they must be regarded as in the main products of excre- 
tion, though the author is of opinion that they may in certain cases take 
part in the formation of food-materials for the plant. They have not, at 
present, been detected elsewhere in the vegetable kingdom. 
* Ann. Sci. Phys. et Nat., iii. (1897) pp. 514-5. 
t Ann. of Bot., xi. (1897) pp. 307-26 (1 pi.). 
% Ber. Deutsch. Bot. Gesell., xv. (1897) pp. 303-20 (1 pi.). 
§ Kosmos, xviii. pp. 382-98 (2 figs.) (Polish). See Bot. Centralbl., lxx. (1897) 
p. 50. 
