ZOOLOGY A.ND BOTANY, MICROSCOPY, ETC. 
71 
and, in this and other respects, the phenomena thus brought about 
artificially are compared to the nyctitropic movements of leaves. The 
authors consider that the results of these experiments confirm Charles 
Darwin’s theory that all growth curvatures are developments or 
exaggerations of circumuutation. 
(4) Chemical Changes (including Respiration and Fermentation). 
Oil-splitting and Glycoside-splitting Ferments.* — A further inves- 
tigation of the action of these two kinds of ferment in the plant leads 
Dr. W. Sigmund to the conclusion that no sharp line can be drawn 
between them, some of the ferments hitherto regarded as belonging to 
one of these two classes being able, in certain cases, to perform the 
function usually attributed to the other. 
7. General. 
Relationship between Plants and Snails. f — Sig. L. Piccioli enu- 
merates the various protective structures in plants to prevent destruction 
by snails. One of the most important of these is tannic acid, which 
occurs in large quantities in the leaves of many leguminous plants, in 
many plants belonging to the section Cynarocephalae of Composite, in 
several genera of Rosaceae, in several species of Sambucus , in Humulus 
Lupulus , Cannabis sativa , Ac. The latex of many Composita3, &c., is also 
protective, also the essential oil contained in the glands on the leaves 
of Labiatae, of Juglans regia , Eucalyptus globulus , &c., and the raphides 
in the cells of Arum maculatum , species of Cactus , and many others. 
The author believes the Gastropoda to be endowed with a distinct sense 
of smell. Purely mechanical defences, such as a weft of hairs, spines, 
Ac., occur in many plants, but are of less importance than the chemical. 
B. CRYPTOGAMIA. 
Cryptogamia Vascularia. 
Embryology of Angiopteris.j;— Prof. J. B. Farmer has studied the 
development of the embryo of Angiopteris evecta. The prothallium 
resembles the thallus of Anthoceros rather than the prothallium of most 
ferns, but is somewhat larger, and orbicular in shape. The antherid is 
formed from a superficial cell of the pro thallium, which divides, by a 
wall parallel to the surface, into an outer shallow and an inner cubical 
cell. The former gives rise to the cover-cells by walls at right angles 
to the free surface, while the inner one originates the antherozoid 
mother-cells by successive bipartitions. The antherozoids are large, 
and are formed from the nucleus of the mother-cell. The antherids are 
distributed irregularly on both surfaces of the prothallium ; the arche- 
gones occur on the lower surface only. 
The basal wall of the fertilized oosperm is formed, as in Isoetes and 
Equisetum, at right angles to the axis of the archegone ; the further cell- 
* SB. K. Akad. Wiss. Wien, ci. (1892) pp. 549-59. Cf. this Journal, 1891 
p. 221. 
t Bull. Soc. Bot. Ital., i. (1892) pp. 338-45. Cf. this Journal, 1891, p. 499. 
I Ann. Bot., vi. (1892) pp. 265-70 (1 pi); and Proc. Roy. Soc., li. (1892) 
pp. 471-4. 
