December 2, 1915] 



NATURE 



111. 



fardalina) and the red locust (Pachytylus capensis). 

 The author briefly and lucidly reviews the previous 

 records of such visitations, from 1653 to the present 

 day. From the data thus collected he is enabled to 

 show that these outbreaks follow close on the heels 

 of seasons of prolonged drought, and is further always 

 associated with large tracts of naturally arid country, 

 where the rainfall is both scanty and erratic. He 

 ^nves valuable notes on the life-histories of these in- 

 sects, and on their natural enemies. In regard to 

 the brown locust, he is of opinion that the eggs pre- 

 serve their vitality for years in the absence of adequate 

 moisture for their development. If indeed this be the 

 lease, it is certainly very remarkable. 



The ravages of locusts forms the subject of a special 

 illetin issued by the United States Department of 

 Agriculture (No. 293). This deals with the " Grass- 

 jpper Outbreak in New Mexico during the Summer 

 1913." The species mainly concerned is the long- 

 anged grasshopper (Dissostera longipennis). The 

 luthor, Mr. Harrison E. Smith, traces the history of 

 lis insect in America, and then proceeds to describe 

 the life-history in detail. Among its numerous enemies 

 )irds, lizards, and toads are the most effective in keep- 

 ig down its numbers. No less important are a para- 

 sitic fly {Sarcophaga kellyi), and sphecid and bembecid 

 i?asps. The former deposit living larvae upon the 

 idults, which are then doomed to be devoured alive, 

 ^hile the wasps paralyse large numbers and store 

 ;m to serve as food for their young. But in spite 

 >f the ravages of their enemies it seems necessary 

 resort to artificial remedies to exterminate these 

 »sts. Of these the most effective is that afforded by 

 mixture of Paris green, bran, and molasses, to which 

 fis added the skin and pulp of oranges or lemons. 

 [The effect of the wholesale distribution of poison on 

 I other animals is not stated. 



Two species of the genus Rhizoctonia of some 

 ^economic importance in India form the subject of a 

 paper by Messrs. Shaw and Ajrekar in Memoirs of 

 the Department of Agriculture in India, vol. vii., 

 No. 4. These are R. napi, West, which was found 

 as a virulent disease on mustard and on grasses, and 

 R. destruens, Tass., on potatoes. Betel vine {Piper 

 betle) is also seriously affected by this latter fungus in 

 Bengal and Bombay. R. napi is an omnivorous para- 

 site, and was found to attack all plants in the vicinity 

 of the mustard plot where it first appeared. Methods 

 of soil sterilisation and for disinfecting potato tubers 

 are given. It seems possible that under the name 

 Rhizoctonia we are dealing with an artificial group 

 of which the different species are vegetative stages of 

 widely separate fungi with morphological similarities, 

 and a study of R. napi strengthens this suggestion, 

 since it appears that it is merely a sclerotial stage of 

 a Botrytis. The paper is illustrated by six plates. 



The genus Antennaria is represented in Greenland 

 by several well-marked species, though usually con- 

 sidered to be merely forms of A. alpina, a species 

 closely allied to the well-known A. dioica of Europe. 

 M. P. Porsild, in Meddelelser om Gronland, li., de- 

 scribes and figures four species, of which he has made 

 NO. 2405, VOL. 96] 



a close study at the Danish Arctic Station at Disko, 

 Greenland. A. alpina is a widely distributed Arctic 

 alpine^ form extending into North America. A. 

 glabrala appears to be confined to Greenland. A. 

 groenlandica is a rare plant met with in southern 

 Greenland, and probably American in origin, and A. 

 intermedia, also a rare species, is found chiefly near 

 Disko, where it may form large colonies. It is of 

 interest to notice that A. alpina has been found at an 

 altitude of 4100 ft. on Jensen's Nunatakker, in 

 southern Greenland. All the species set seed freely, 

 but they are apparently apogamous, as thiere is no 

 record of any male plants having been seen in Green- 

 land. 



The jand forests of the Punjab are spread over 

 the arid, alluvial plains, where, as a rule, the rainfall 

 does not exceed 10 in. The area covered is some 

 3500 square miles, and the three dominant trees are 

 jand (Prosopis spicigera), wan {Salvodora oleoides), 

 and karil {Capparis aphylla). Of these jand is a fairly 

 valuable tree of local importance. It is chiefly remark- 

 able owing to the length of its tap-root, specimens 

 having been found with a tap-root as much as 84 ft. 

 in length descending vertically to a depth of 64 ft. 

 Mr. B. O. Coventry, in his paper on these forests in 

 the Indian Forester, vol. xli.. No. 9, 1915, points out 

 that this tap-root enables the tree to obtain its water 

 from the permanent water supply in the subsoil. 

 Doubtless at one time the jand lived in a region 

 liable to floods, since it has been found that no natural 

 regeneration occurs in the jand forests, though in 

 irrigated or flooded districts the jand is reproduced 

 readily from seed. It seems probable that the ex- 

 planation of the long tap-tf)Ots is due to the effort 

 on the part of the tree to keep pace with the gradual 

 lowering of the water table in the soil, resulting from 

 the lowering of the river-beds by erosion. 



Owing to the large number of papers of funda- 

 mental significance to agriculture that are awaiting 

 publication in the journal of Agricultural Research, 

 the Secretary of the Department, Washington, 

 announces that, beginning with vol. v., a number 

 of the journal will appear each week. Since Russell 

 and Hutchinson put forward their theory of the in- 

 fluence of protozoa upon soil fertility, rhuch work has 

 been done in America in the field opened out by their 

 researches. In No. 3 of the new volume, Kopeloff, 

 Lint, and Coleman describe a method for quantita- 

 tively separating protozoa into classes as flagellates, 

 small ciliates, and large ciHates. The culture solution 

 under exarhination is filtered through from one to 

 five thicknesses of sterile filter-paper. The protozoan 

 content in the filtrates passing through in the first 

 minute is then recorded in triplicate by the authors' 

 method described in a previous paper. The filtrates 

 are further incubated to allow the development of 

 any encysted forms. By treating soil and hay in- 

 fusions in this way, it was found that the large 

 ciliates are unable to pass through filter-paper at all, 

 as noted by Russell and Hutchinson, while three 

 thicknesses of the paper were required to remove all 

 the small ciliates. No protozoa were found in the 

 filtrate from five papers. In this way, mass cultures 



