208 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Tropical Foliage.* — Prof. G. Haberlandt contrasts the characteristics 
of the foliage in the tropics, as observed at Buitenzorg in Java, with 
that of temperate climates. The chief peculiarity observed was the 
much smaller amount of transpiration. The mechanical aids for this 
diminution of transpiration are a thick-walled strongly cutinized epi- 
derm, depressed stomates, and especially a variety of forms of reservoirs 
for water, such as an aquiferous tissue, mucilage-cells, and storing 
tracheids. These perform the double function of preventing the withering 
of the leaves in the hot sunny forenoon, by which assimilation would be 
hindered, and of promoting the distribution during the night of the 
water which is plentifully absorbed through the roots. It is noteworthy 
that these peculiarities are also those which enable a plant to pass from 
a terrestrial to an epiphytic mode of existence. 
Abnormal Leaves.f — Prof. J. Klein has investigated the phenomena 
connected with divided leaves, both in the case of those that are normally 
opposite ( Nerium Oleander , Weigelia rosea , Lonicera fragrantissima , 
L. tatarica , Syringa vulgaris , PJiiladelphus coronarius, Calycanthus floridus, 
Vincetoxicum officinale , Asclepias pulchra ), and those that are normally 
spiral (Morns alba , M. nigra , Ficus australis , Cydonia vulgaris , Pyrus 
amygdaliformis , Pobinia Pseudacacia , Phaseolus vulgaris). The cause of 
the phenomenon differs in different cases. In some it is the result of a 
union of two leaves, and then the number of vascular bundles which 
enter the lamina is double the ordinary number or more ; in others it is 
the result of division, and then the number of vascular bundles is normal, 
although there is no external difference between leaves belonging to the 
two categories. The first of these two malformations is a frequent 
result of lopping, and is especially common in Morus and Lonicera 
fragran tissima. 
Petiole of Phanerogams. I — M. L. Petit points out that, notwith- 
standing the variations in the course of the vascular bundles in the 
leaf-stalk, there are only a small number of types, and that these are 
characteristic of whole families, or of genera. In Monocotyledons and 
Gymnosperms the bundles are never united into a common ring or arch, 
but remain distinct. The Marantacese are characterized by oblique cells 
at the end of the leaf-stalk, the Dioscoreacese by layers of phloem on each 
side of the bundle. In the Cycadese the configuration of the vessels on 
a transverse section of the leaf stalk serves as a character for certain 
genera. 
Action of the Humidity of the Soil on the Structure of the Stem 
and Leaves.§ — According to M. A. Oger, if plants of the same species 
are growir, some in a very dry, others in a very moist soil, other con- 
ditions being the same, those which are grown in moist soil will assume 
all the characters — a large size and branching habit, great length of 
the upper leaves, lax inflorescence, increase in number of the vascular 
bundles, &c. — characteristic of plants which grow naturally in moist 
situations. The experiments were made on Lapsana communis , Sonchus 
* SB. K. Akad. Wiss. Wien, ci. (1892) pp. 785-816. 
t Jahrb. f. Wiss. Bot. (Pringsheim), xxiv. (1892) pp. 425-98 (6 pis. and 3 figs.). 
X Actes Soc. Linn. Bordeaux, xliii., 100 pp. and 4 pis. See Bot. Centralbl.. lii. 
(1892) p. 65. § Comptes Rendus, cxv. (1892) pp. 525-7. 
