550 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
of cases, as a means of adaptation to changed conditions, especially to a 
drier climate. From this] are derived the unifoliolate forms through the 
disappearance of the lateral leaflets, the imparipinnate by multiplication 
of the lateral leaflets. 
Special attention is paid to the structure of the leaves in Mimoseae, 
and especially in the genus Acacia , with its very large number of species 
in which the leaves are replaced by phyllodes. All the phyllodineous 
species of Acacieae are heterophyllous ; but the heteropliylly is usually 
limited to the youngest stages of the seedlings, and the appearance of 
pinnate leaves must be regarded as a phenomenon of reversion. The 
reduction of the leaves is commonly accompanied by the appearance of 
wings on the stem, which may be metamorphosed lower leaflets or meta- 
morphosed stipules. They serve, like the leaves, as organs of assimila- 
tion. 
Spotted Leaves.* * * § — Prof. G. Arcangeli refers to a number of other 
instances (in addition to Arum italicum) of plants with spotted leaves, 
and suggests that the variegation may serve different purposes in differ- 
ent cases, viz. : — in promoting the functions of transpiration and respi- 
ration ; in protecting the assimilating tissue from too intense radiation ; 
in defending the parts affected from the injurious effects of cold ; in 
promoting the visits of pollinating insects ; in contributing to the beauty 
and elegance of the leaf, and thus promoting the dissemination and dif- 
fusion of the species. 
Hydathodes of Tropical Plants. — Herr S. H. Koorders + describes the 
adaptation of the calyx for the exudation of water in 13 tropical species, 
of which 6 belong to the Bignoniaceae, 3 to the Solanaceae, 2 to the 
Verbenaceae, and one each to the Scrophulariaceae and the Zingiberaceae. 
The exudation always takes place on the inner surface of the calyx, 
sometimes also on the outer surface of the corolla. The hydathodes are 
multicellular capitate hairs, the surface of which is covered by a cuticle 
through which the exudation takes place. The water remains in the 
calyx throughout the development of the flower, and in one case till the 
fruit is formed ; during this period the floral organs are covered with a 
coat of mucilage like the young organs of aquatic plants. On the inner 
side of the calyx the stomates are very few or entirely wanting. Bacteria 
or fungus hyphae were invariably found within the water-calyx, but 
never more than one kind in the same species. There is the closest con- 
nection between hydathodes and nectaries, these organs differing only in 
the nature of their secretion. The same trichome may perform different 
functions at different periods. 
Herr H. Hallier j calls attention to another example of a water-calyx 
in Leea amabilis, belonging to the Ampelideae. 
Adhesive Discs of Ercilla.§ — Mr. J. H. Burrage describes the adhe- 
sive discs borne immediately above the axils of the leaves in Ercilla 
volubilis, belonging to the Phytolaccaceee. They have several points in 
common with those of the Virginian creeper, attaching themselves to a 
* Bull. Soc. Bot. Ital., 1897, pp. 198-203. Cf. this Journal, ante , p. 217. 
t Ann. Jard. Bot. Buitenzorg, xiv. (1897) pp. 354-4:77 ( 7 pis.), 
t Tom. cit., pp. 241-7. 
§ Journ. Linn. Soc. (Bot.), xxxiii. (1897) pp. 95-102 (1 pi.). 
