172 SUMMARY OF CURRENT RESEARCHES RELATING TO 



stomata, and those usually associated with floating leaves. This con- 

 firms the view expressed in a previous paper, that the " trichter type '" 

 is the transition stage between the other two types. Moreover, since 

 the normal type is the only one found in cotyledons, and in young 

 leaves which, on attaining maturity, adopt either the " trichter " type or 

 that found in floating leaves, it would seem as if the normal type is the 

 most primitive and gives rise to the other two types. It is of interest 

 to note that although the Crassulaceas are so closely allied to the Saxi- 

 fragaceag, their stomata are all of the normal type. 



The internal and external conditions which induce modifications of 

 the stomata, such as those described, have yet to be discovered. 



Structure of Tropical Wood.* — A. D. Hopkinson describes the 

 anatomy of various species of tropical wood ; transverse and longitudinal 

 sections were examined, and the descriptions include the wood paren- 

 chyma, the vascular bundles, the cambial tissues, the medullary rays, 

 and the colour. The species studied are as follows : — Pentaclethra 

 macrophylla, Conla edulis, Alstonia congensis, Sterculia tragacantha, 

 AlUzzia Wehvitschii, Pterocarpus Soyauxii, Staudtia hamerunensis, 

 Xylopia striata^ StercuUa oUotiga^ Rhizophora mangle, Kichxia elastica, 

 Piptadenia africana, Terminalia superba, Lophira alata, ChloropJwra 

 excels a. 



Immature Leaves of Woody Plants.! — R. Schramm has investi- 

 gated the anatomy of the young leaves of a large number of trees and 

 shrubs commonly found in Germany. The following natural orders 

 were studied : — Fagacese, Ulmacese, Betulacese, Aceracese, Oleacese, 

 Tiliaceee, Caprifoliacete, Cornaceae, Berl^eridacese, and Scrophulariacese. 

 In all cases the leaves of the seedhngs differed in structure from those 

 of the adult plants, being specially adapted to early conditions of 

 growth. The full-grown leaves are the result of a development ex- 

 tending over several years. The youth-form of leaf is constant and 

 hereditary, and bears some resemblance to that of leaves grown entirely 

 in the shade ; this resemblance is strong in Fagus, less so in Acer, 

 Carpimis, and Tilia. Shade-leaves may be regarded as a perpetuated 

 and more highly developed youth-form of leaf, resulting from a response 

 to special environment. By strong insolation and its accompanying 

 increase in temperature, the youth-form of leaf may be induced to 

 decrease its relative amount of spongy parenchyma, and to assume 

 more rapidly the adult form of leaf. 



Germination, Development, and Anatomy of the Cistineae.J — R. 

 Gaume has studied several species of this family, and finds that they 

 exhibit great uniformity of structure. The outer integument of the 

 seed is reduced to a thin transparent membrane, but the inner is always 

 composed of several layers of cells, forming an outer crustaceous and 

 an inner membranous layer. All the seeds, especially of perennial 

 species, germinate quickly and easily. The embryo is curved in Heli- 



* Beih. Bot. Centralbl., xxix. 2te Abt. (1912) pp. 441-56 (24 figs.). 



t Flora, iv. (1912) pp. 225-95 (3 pis.). 



X Rev. Gen. Bot., xxiv. (1912) pp. 273-295 (12 figs.). 



