Floristik, Geographie, Sj^stematik etc. 425 



lees, Sans que l'auteur precise toujours s'il s'agit d'urie race, d'une 

 Variete ou d'une espece nouvelle. On peut cependant indiquer parmi 

 ces dernieres celles dont il est donne (en frangais) une diagnose 

 süffisante: Cusctita Coriariae Sen. et Pau, qui vit exclusivement sur 

 Coriaria niyrtifolia, Cusctita Ericae Sen., „race ou espece qui croit 

 de preference sur V Erica arborea/' Dianthiis Cadevallii Sen. et Pau, 

 Aster harcmonensis Sen., annonce comme hybride en 1912. Les 

 nouveaux hybrides decrits sont: X Xanthimn Sallentii (X. Strurna- 

 rium X ^- barcinonense) Sen., Cad. et Pau, X Galium Viciosoruni 

 [G. verum X G. nutritinmm) Sen. et Pau, X Carduus Nuriae {C.pe- 

 trophilus X C. crispus) Sen. et Pau, X Salvia Domenechii (S. muUi- 

 fida X •^- clandestina) Sen., X Lavandula Cadevalli {L. Staechas X 

 L. pedunculata) Sen., X Erigeron barcinone)ise {E. corotiopifolium X 

 Conysa ambigua) Sen. J. Offner. 



Shreve, F., The Direct Effects of Rain fall on Hygrophi- 

 lous Vegetation. (Journ Ecol. IL 2. p. 82-98. 1 pl. 1914.) 



Features of tropica) Vegetation, such as hydathodes, drip-tips 

 of leaves, velvet surfaces, have been interpreted mainly as biological 

 adaptations of value to the plant (Stahl, Haberlandt, Jungner, 

 Holtermann, etc.). Shreve has endeavoured to apply the same 

 interpretations to the tropical Vegetation of Jamaica, with the result 

 that "casual Observation and a vivid imagination" are suggested as 

 responsible for at least some of the interpretations, and he tries to 

 arrive at a true valuation of these phenomena. by a study of the 

 normal physiology of tropical plants and of the infiuence on them 

 of physical factors. 



Only the principal points of the author's summary can be given 

 here, but the original paper contains details of experiments and 

 observations made, as well as representative species in Jamaica. 

 Hydathodes, drip-tips, and other supposedly adaptational structures 

 in hygrophilous foliage fail to perform the functions attributed to 

 them, and they are poorly represented in the Jamaican rain-forest. 

 With the exception of Gramineae and Cyperaceae, only 4 common 

 flowering plants have hydathodes, 2 spp. of ferns have functional 

 hydathotes, but a larger number have non-functional. Exceptionally 

 heavy rain (e. g. 5 days, 201 cm.) causes injection of the intercel- 

 lular Spaces in thin leaved herbaceous plants, including Diplasium 

 altissimum, which has functional hydathodes, no leaves of trees or 

 shrubs were seen to be even partially injected. Plants with drip-tips 

 are relatively uncommon in the rain-forest, as are also those with 

 velvet surfaces, variegated foliage, and drooping juvenile leaves. 

 Experiment (tables given) fails to confirm the view as to the Utility 

 of the drip-tip in drying the leaf-surface (e g. in Pilea grandifolia). 

 Epiphyllous algae, lichens, etc. are abundant on leaves of every 

 type, including the few with drip-tips; their occurrence depends 

 solely on the moisture conditions surrounding the plant, e. g. in 

 narrow Valleys where humidity is high and constant, and where 

 sunlight hardly dries the foliage; on ridges and peaks epiphyllous 

 plants are exceptional. Surface wetness does not lower the tempe- 

 rature of leaves sufficiently, under rain-forest conditions, to affect 

 rate of transpiration. Surface wetness of leaves lowers their intake 

 of water from the stem, partly through the stoppage of cuticular 

 transpiration and partly through the absorption of water by the 

 lightly cuticularised epidermis. The Substitution of the intake of 



