NOTES AND ABSTRACTS. 



155 



however, is criticized as a general scheme of classification of biogeography regions. 

 The role of soil and. atmospheric moisture is of vital importance, and is potent 

 in determining the areas of the principal vegetational regions of the globe. 



At the Desert Laboratory, Tucson, Arizona, much useful work has been done 

 in determining the distribution of plants as controlled by the temperature and 

 other factors. The topography of the country renders it of extreme interest 

 and value for investigations of this nature. From the surrounding desert ascend 

 three ranges of mountains, rising to 9,000 feet. The slopes present rapid changes 

 of climate and vegetation from Cacti and thorn-shrubs at the base, through 

 junipers and oaks, to forests of yellow pine and spruce and fir. The lower limit 

 of the juniper-oak chaparral is about 4,500 feet, that of the pine forest about 

 6,500 feet. Their failure to reach the desert is attributed to the ratio between 

 the soil moisture and the evaporation in the early summer, which is of extreme 

 aridity below 5,000 feet. There is the possibility that some phase of the 

 summer temperature conditions may also operate to limit the distribution of 

 mountain plants at the edge of the desert. 



The upward limitation of the subtropical desert species is attributed to the 

 winter phases of the temperature conditions, as has been determined both by 

 experimental evidence and by correlation of the results with observations of the 

 vertical limits of species. — A. B. 



Drug Plants in England, Collection and Sale of {Jour. Bd. AgrJ^^xi. 

 p. 62, April 1915). — Owing to the shortage of drugs because of the War, the 

 Board of Agriculture suggests that the members of Natural History Societies 

 &c. might usefully co-operate in the collection and sale of drug plants during 

 the present year. Reference is made to the Board's Leaflet 288, which gives 

 information as to the various drug plants, their cultivation and collection. 

 Foxglove, Henbane, Thorn-apple, and Belladonna are the most important 

 species, but many other species are useful. Arrangements should be made 

 previously as to the sale and despatch of plants, and the Board will furnish a 

 list of possible buyers who would supply information as to special requirements. 

 The careful identification of species is emphasized, and the depletion of species 

 in particular localities is deprecated. — G. C. G. 



Eehinocaetus minusculus (Bot. Mag. tab. 8583). — Argentina. Nat. Ord. 

 Cactaceae, tribe Echinocacteae. Herb, succulent, globose, 1-2^ inches across, 

 tuberculated. Flowers rising from the base of the plant, erect, 1 inch across. 

 Petals about 12, bright vermilion. — G. H. 



Echinopanax horridus (Bot. Mag. tab. 8572). — Japan and North 

 America. Nat. Ord. Araliaceae, tribe Schefflereae. Shrub, 3-10 feet high. 

 Leaves palmately 5-9-lobed, 6-10 inches across. Flowers umbellate, arranged 

 in dense globose panicles, pale green. — G. H. 



Echiums from the Atlantic Islands. By T. A. Sprague and J. Hutchinson 

 (Kew Bull. pp. 116-122, 265-267, May, October 1914 ; plates). — A descrip- 

 tive account of the Echiums of the Canary Islands and Madeira, in which Echium 

 giganteum, E. leucophaeum, E. Bond- Spy aguei, E. brevirame, E. aculeatum, E, 

 Auberianum, E. Wildpretii, and E. Perezii are dealt with. E. Bond-Spr aguei 

 and E. brevirame are new species. — F. J. C. 



Electrical Injuries to Trees. By Geo. E. Stone (U.S.A. Exp. Sin., Mass., 

 Bull. 156, Oct. 1914, pp. 1-19; 5 plates and 3 figs.). — This bulletin replaces one 

 published in 1902, and details of new observations since that time have been 

 incorporated in the present edition. 



In towns, both alternating and direct currents are used. They produce 

 different physiological effects, the alternating current being apparently less 

 injurious than the direct. Both, however, at a certain amperage, act as a stimulus 

 and cause accelerated growth and development. The minimum and optimum 

 current strengths differ little in different plants. The maximum current — that 

 necessary to kill a plant — varies considerably. 



The greatest injury, however, consists of local burning and partial destruction 

 of the trees, caused by high-tension line wires. In dry weather little or no leakage 

 from wires occurs, but in wet weather, when a film of water is formed on the 

 bark, more or less leakage occurs, and if the insulation is insufficient, grounding 

 takes place, and burning due to " arcing " results. 



The death of the trees occurs when the polarity in the electric tramways 

 has become reversed, i.e. when the rail is positive and the feed wire negative. 



