ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
659 
“Heterotopic” Plants.* — By tliis term Dr. F. X. Gillot designates 
those plants which are occasionally found on soils apparently very 
different from those on which they normally occur. This apparent 
indifference frequently arises from the observer having taken into 
account only the geological, and not also the chemical nature of the 
soil. It is especially common to find colonies of calciphilous plants on 
a siliceous soil ; and this arises frem the silica being accompanied by 
calcium silicates and phosphates. 
B. CHYPTOGAMIA. 
Cryptogamia Vascularia. 
Leaves of Ferns.f — From a comparison of fossil with recent forms, 
Herr H. Potonie draws the conclusion that the truly pinnate structure 
of the frond of ferns has been derived phylogenetically from an 
archaic dichotomous form. Transitions from one to the other are to be 
observed in fossil forms, while the great majority of the oldest (Palaeo- 
pteridese) exhibit a dichotomous venation with but a small development 
of the central vein. 
Mucilage-Canals of the Marattiacese.j — Mr. G. Brebner, who has 
studied the mode of formation of the mucilage-canals in the Marattiaceae 
( Angiopteris evecta, Marattia cicutse folia, M. alata), finds it to be, with 
but little exception, typically schizogenous, differing in no important 
respect from that of resin-canals ; they are not produced by the muci- 
laginous degradation and death of cells. In the roots of A. evecta no 
mucilage-canals were found, but in their place rows of tannin-sacs. The 
roots of Marattia attenuata possess true mucilage-canals. In the aerial 
roots of some varieties of A. evecta there is in the cortex a ring of 
peculiar mucilage-cavities, which have no secretory epithele, and appear 
to have a schizo-lysigenous origin. 
Development of the Sheath of Equisetum.§ — Herr H. C. Schellen- 
berg contests C. Muller’s theory || that the lines on the leaf-sheaths of 
Equisetum are the result of traction. From observations made on 
E. limosum and Jiyemale, he states that they are formed by the unequal 
growth of the commissure and median plane of the tooth at the base of 
the sheath. The lines are at first narrow, but become subsequently 
broader from the opening of the teeth. 
Sphenophyllacese.l — Prof. G. Arcangeli discusses the systematic 
position of this family, which he regards as having no near affinity with 
.any other group of plants, either fossil or recent. The structure of the 
stem recalls that of the Calamarieae, while the mode of formation of the 
spores presents a greater resemblance to that of the Lycopodineae. 
* Bull. Soc. Bot. France, xli. (1895) Sess. Extraord., pp. xvi.-xxxv. 
f Ber. Deutsch. Bot. Gesell., xiii. (1895) pp. 244-57 (3 figs.). 
X Journ. Linn. Soc. (Bot.), xxx. (1895) pp. 444-51 (1 pi.). 
§ Ber. Deutsch. Bot. Gesell., xiii. (1895) pp. 165-74 (1 pi.). 
|| Cf. this Journal, 1889, p. 256. 
Nuov. Giorn. Bot. Ital., ii. (1895) pp. 261-72. Cf. this Journal, 1894, 
pp. 374, 595. 
2x2 
