214 
SCTMMARY OF CURRENT RESEARCHES RELATING TO 
tendrils of the Passifloracem. The brothers Bravais considered the 
tendril to be an accessory bud ; Masters held that it was the result of 
the partition of the floral peduncle ; while Eichler described the tendril 
as an axillary branch of the leaf. The author has made most of his 
observations on Passiflora holosericea, and draws the conclusion that the 
tendril of the Passifloraceae represents a modified axillary branch. 
Protection of Foliage against Transpiration.* — Prof. A. F. W. 
Schimper has studied this subject, especially in relation to the flora of 
Java. The protection against excessive transpiration afforded by the 
reduction of the surface and of the intercellular system, by a coating of 
resin or wax, by a thick cuticle, &c., is required not only by plants 
which grow in very dry situations, but also by halophytes, by Alpine 
plants, and in the colder temperate zones, by evergreen woody plants. 
This xerophilous character of the foliage is exhibited by the coast 
vegetation of Java — consisting of the mangrove, Nipa fruticans , 
Casuarina , Cycas circinalis , species of Pandanus , Ipomsea pes-caprse, &c., 
even when the soil on which they grow is frequently flooded. This 
structure is rendered necessary by the fact that the presence of salt in 
the substratum hinders the absorption of water, and that concentrated 
saline solutions in the green cells retard assimilation. 
The same xerophilous character is presented by the alpine flora of 
Java, although the mountain-tops are never covered with snow, and the 
temperature is throughout the year favourable for vegetation. The 
principal determining causes appear to be here the rarity of the air 
and the powerful insolation, both of which have a tendency to promote 
transpiration. The evergreen trees and shrubs of temperate climates, 
such as the box, holly, ivy, conifers, &c., exhibit similar protective 
adaptation against excessive transpiration (and not against cold), in the 
thick cuticle, depressed stomates, &c. 
Abnormal Leaves of Vicia sepium.f — M. W. Russell describes a 
modification in the structure of the leaves of Vicia sepium in con- 
sequence of the puncture of an insect, causing the transformation of the 
leaflets into ascidia. The puncture brings about an inequality in the 
growth of the cells of the two surfaces of the leaf, causing a folding of 
the leaflets on its median vein as on an axis. 
Influence of the Moisture of the Air on the Production of 
Spines.J — M. A. Lothelier has studied the causes which accelerate and 
retard the production of spines in two plants, namely Berberis vulgaris 
and Cratsegus oxyacantlia. The result of his observations is that the 
hygrometric state of the air exercises a marked influence on the pro- 
duction of spines in both the plants named. Dry air accelerates their 
production, while humidity retards it ; and the internal differences 
correspond to the exterior. In a section of a spine exposed to moist air 
the vessels of the xylem are few in number, and the pericycle is not 
lignified ; in dry air the xylem forms a continuous ligneous circle, and 
the pericyle is also lignified. 
* SB. K. Preuss. Akad. Wiss., 1890, pp. 1045-62. 
t Rev. Gen. de Bot. (Bonnier), ii. (1890) pp. 481-9 (4 figs.). 
j Bull. Soc. Bot. France, xxxvii. (1890) pp. 176-8. 
