Septembek 25, 1896.] 



SCIENCE. 



435 



while many embryos are to be nourished 

 in the earlier cases, there are but one or 

 two in the later. The biological signifi- 

 cance of this result is so well known as to 

 need no discussion here. 



When we come to an application of what 

 we know of the compound ovary to system- 

 atic botany, it appears to me that the fol- 

 lowing conclusions are warranted : 



(a) The apocarpous plants are to be re- 

 garded as lower than those which are syn- 

 carpous, and in a natural arrangement the 

 former must precede the latter. 



(b) We must carefully distinguish be- 

 tween ovaries which are primitively simple 

 and those which have become simplified 

 from a more complex structure. In these 

 cases the first indicate a lower and the 

 second a higher position in the natural 

 system. 



(c) Grasses, Sedges, etc., in which the 

 ovaries are simplified from the compound 

 type are not the lowest of the Monocoty- 

 ledons. 



(d) Willows, Oaks, Walnuts, etc., with 

 their apparently simple flower structure, 

 are not to be regarded as among the lowest 

 of the Dicotyledons. 



The influence of rainfall upon leaves: By 



D. T. MacDougal. 



The first recognition of the influence of 

 rainfall upon leaf forms was that given by 

 Eidley in his Flora of Eajang, and an ex- 

 ploitation of the subject was made by Stahl^^ 

 in 1893. Since the publication of StahPs 

 work, Jungner has carried on a great 

 amount of observational work of doubtful 

 value and has made some attempts to pro- 

 duce rainfall characters in leaves experi- 

 mentally. The rainfall characters of leaves 

 recognized by these workers are as follows : 

 Attenuated apices, entire margins, glossy 

 appearance of the upper surface of the 1am- 

 inse, coupled with a ready adhesion of wa- 



*Ann. d. Jard, bot. d. Bintenzorg, 1893. 



ter ; deepened furrows above ribs, pendant 

 positions of the laminae and enlargement of 

 the pulvini. It is to be noted, of course, 

 that in no one species do all of the above 

 characters appear, and furthermore that 

 only a few of those named have been in- 

 duced in leaves experimentally. Jungner 

 was able to cause the glossy appearance of 

 the upper surface of the laminae and its ad- 

 hesion to water, and a pendant position of 

 the entire leaf in a few plants by experi- 

 mental methods. 



The curvature of tendrils: By D., T. Mac- 

 Dougal. 



The curvature of tendrils in response to 

 a contact stimulus is due to the contraction 

 of certain cells on the concave side of the 

 organ. These cells show great specializa- 

 tion in form, size and arrangement, and are 

 markedly difierent from similar elements 

 on the convex side. The protoplasm of the 

 external cells exhibits some -specializations 

 and appears to correspond in density with 

 the degree of sensitiveness. It has been 

 found that the eflects of a stimulus are not 

 transmitted more than two centimeters 

 from the point of its reception. The prev- 

 alent idea that the coiling of the free por- 

 tion of a tendril is stimulated by the en- 

 gagement of the tip with any solid object 

 is found to be false, since the curvature of 

 the organ in response to a stimulus and the 

 coiling of the free portion are entirely in- 

 dependent processes; the latter ensues on 

 maturity only, as may be seen if the tip of 

 a young tendril is attached to a support. 



Relation of the growth of leaves to the carbon 

 dioxide of the air : By D. T. MacDougal. 

 A large number of experiments were per- 

 formed in which leaves of Ariscema triphyl- 

 lum, Calla palustris, Lilium splendidum, Tril- 

 lium erectum and T. erythrocorpum, Isopyrum 

 biternatum, Oxalis floribunda and 0. vesperti- 

 lionis, Justicea sp. Hibiscus rosa-sinensis, Zea 

 mais and Phoenix dactylifera were allowed to 



