NOTES AND ABSTRACTS. 



251 



the functions which have been ascribed to these products. Tyndall's view, 

 that they served to check excessive heating by the opacity of their vapour 

 to ultra-red rays, is improbable ; the effect would be null during wind, 

 which accompanies the intense midday heat of deserts, and though it 

 might be thought to reduce cooling by radiation on calm clear nights, 

 the amount of vapour present under natural conditions is too small to 

 produce Tyndall's opacity. H. Dixon's view, that the function of essential 

 oils is to check transpiration, is examined and found to depend on their 

 presence in vapour, which is inoperative in quantities which are not 

 harmful ; the action observed is due to the injection of the intercellular 

 spaces, so that evaporation is limited to the stomates instead of extending 

 to the whole of these spaces. The author regards the function as protec- 

 tive against omnivorous plant-feeders, such as mollusks and herbivorous 

 mammals, and justifies his view by a careful series of experiments. 

 Incidentally he refutes the supposed protective function of the mimicry 

 of the Stinging-nettle by the Dead-nettle, which is a priori improbable, 

 as herbivora select mainly by smell, not sight, and non-existent, as rabbits 

 and snails have no hesitation in feeding on the latter and rejecting the 

 former. Haberlandt's explanation of the mechanism of the superficial 

 glands of Btttacece is dealt with at some length and extended by a descrip- 

 tion of these in Dictamnus (Dittany). — M. H. 



Eucalyptus cultivated in the United States. By Alfred James 

 McClatchie, M.A. (U.S.A. Dep. Agr. Bur. Forestry, Bull. n. 35, 1902).— 

 It will be news to many that the Australian Eucalypts are more 

 extensively planted than any other exotic forest tree in the South- 

 Western United States. 



In this excellently got -up account of the fully fifty species of 

 Eucalyptus cultivated in America they are viewed mainly from the stand- 

 point of their usefulness, ornamental qualities being, however, incident- 

 ally discussed. The uses of these trees are so many that to discuss all 

 would be quite out of place in an abstract like the present. Suffice it to say 

 that, whether for the value of the timber produced, suitability of the trees 

 for dry arid situations, or as a source of many valuable gums, resins, and 

 oil, they probably stand unrivalled amongst foreign introductions to the 

 American coast. 



The illustrations of the various species render this bulletin of great 

 value for reference purposes, while the ample descriptions combine to 

 place the work as second only to the scholarly " Eucalyptographia " of 

 Baron Ferdinand von Muller. — A. D. W. 



Eupatorium petiolare. By Ed. Andre (Rev. Hort. Feb. 16, 1903, 

 p. 77). — A new introduction from Mexico, highly recommended as a 

 winter-flowering shrub; not hardy; flowers white, in panicles, but ap- 

 parently rose-tinted, owing to abundance of pink threads which appear 

 between the buds. L Delicately perfumed like the winter Heliotrope 

 (Nardosmia fragrans). — C. T. D. 



Euphorbia obesa. By Sir J. D. Hooker (Bot. Mag. tab. 7888).— 

 Nat. ord. Buphorbiacea, tribe Euphorbiece. Native of South Africa. 



