152 



NATURE 



[August 9, 1900 



two Gold Pheasants {Thaumalea picta) from China, a Pheasant 

 (Phasianus cokhicus), five Barn Owls (Strix flaminea), British, 

 purchased; a Japanese Deer (Cerviis sika), born in the 

 Gardens. 



OUR ASTRONOMICAL COLUMN. 



Comet Borrelly-Brooks (1900 i5).— Several observations 

 of this comet are announced. The comet is at present easily seen 

 with a small telescope, but is becoming fainter. 



Ephemeris for 12/1. Berlin Mean Tune. 

 1900. R.A. Decl. Br. 



During the week the comet passes rapidly northwards from 

 a Persei, across into Camelopardus, and then near the boundary 

 of this constellation and Cassiopeia. Its path is at present so 

 nearly linear that it may be found by sweeping along the 

 direction formed by the stars ir, k and a Persei. 



Ephemeris of Comet 1894 IV. (Swift).— Mr, F. H. 

 Seares sends the following search ephemeris for the assistance 

 of interested observers : — 



Ephemeris for 12/2. Berlin Mean Time. 

 1900. R.A. Decl. 



h. m. s. o / 



Aug. 8 ... 15 57 20 ... -24 32-8 

 12 ... 15 59 31 ... 360 



16 ... 16 2 ID ... 40'2 



20 ... 16 5 17 ... 454 



24 ... 16 8 50 ... Sf4 



28 ... 16 12 50 ... -24 58-1 

 Variable Stars in Clusters.— i¥rt;»a;vi' College Observ- 

 atory Circular (No. 52) contains the results of the measures of 

 a set of photographs of the star cluster Messier 3 (N.G.C., 

 5272). This object is so low in the sky at Arequipa, and the 

 stars so faint, that satisfactory photographs of it could not be 

 obtained with the 13-inch Boyden refractor with exposures less 

 than 90m. The rate of increase of the light of many of 

 these stars is extremely rapid, and in order to determine such 

 change with the greatest precision, it is necessary to have 

 photographs taken with short exposures. Accordingly, at 

 Prof. E. C. Pickering's request, Prof. J. E. Keeler has taken 

 a series of excellent pictures of the cluster with the 3-foot 

 Crossley reflector of the Lick Observatory. The first of these 

 had an exposure of 60m., while twenty-four others were ob- 

 tained with exposures of lom. each. Prof. Bailey has ex- 

 amined these photographs very carefully, devoting attention 

 specially to three of the variable stars. It has previously been 

 stated {Circular No. 33) that the proportion of variable stars 

 is greater in this cluster than in any other object of the same 

 class. 



The periods of the three variables were found to be : No. 11, 

 I2h. 12m. 25s.; No. 96, I2h. cm. 15s. ; No. 119, I2h. 24m. 31s. 

 The variations were recorded for intervals of Sm., and are 

 given in a table. From this it appears that the total increase of 

 light takes place in the case of No. 11, within 70m. ; No. 96, 

 within 60m. ; and No. 119, within 80m. The greatest 

 rapidity of increase of light occurs in the star No. 96, which 

 increases during 5m. at the rate of at least 25 magnitudes 

 per hour, and during 30m. at the rate of more than 2"o magni- 

 tudes per hour. This rate of change appears to be the most 

 rapid of any known variable. The Algol variable U Cephei, 

 which perhaps undergoes the most rapid change of any variable 

 not found in clusters, changes at the rate of about i "5 magni- 

 tudes per hour during about 30m. of its period. In all these 

 stars the rate of change is relatively slow near the beginning and 

 end of the period of increase. In No, 96 the increase is about 

 ten times as rapid as the decrease. Generally speaking, the 

 lengths of period and form of light curves of these three stars 

 are similar to those of the variables in the clusters Messier 5 and 

 ui Centauri {Astrophysical Journal, vol, x. p. 255). 



NO. 1606. VOL. 62] 



RECENT INVESTIGATIONS ON RUST OF 

 WHEA T. 



"D UST, or mildew, is familiar to the agriculturist as a 

 disease destructive to wheat and other cereals, and to the 

 botanist as the subject of important researches relating to fungi. 

 It was known in times of antiquity, as shown by numerous 

 references indicating its destructiveness. Virgil says, " Soon, 

 too, the corn gat sorrow's increase, that an evil blight ate up 

 the stalks" (" Georgics," i. 150-1). In Britain, it is stated that 

 " mildew of wheat-plants has been known for over 300 years, 

 according to the records" ("Report on Mildew on Wheat 

 Plants, 1892," Board of Agriculture, 1893, P- 25). Shake- 

 speare ascribes it to " the foul fiend Flibbergibbet " {King Lear, 

 Act iii. Scene 4). The works on husbandry of Hartlib (1655) 

 and Jethro TuU (1731) refer to it. The connection of rust of 

 cereals with a specific fungus is generally ascribed to Fontana 

 (1767), and Persoon, after further investigation, in 1797 named 

 the fungus Puccinia graininis. An account of rust, with illus- 

 trations of the Puccinia, by Sir J. Banks in 1805, is apparently 

 the first important paper on the rust and its fungus in Britain. 

 Since then the epidemic has been the subject of many papers, 

 and of, at least, three organised inquiries. The historical side 

 of the subject is conveniently summarised by Worthington G. 

 Smith ("Diseases of Crops," London, 18S4, Chapter xxv.), by 

 C. B. Plowright (" British Uredinei^ and Ustilaginese," London, 

 1889, p. 46), and in the Board of Agriculture report (" Report 

 on Mildew on Wheat Plants, 1892," Board of Agriculture, 1893, 

 P- 25). 



Rust of wheat occurs throughout Britain, especially in the 

 wheat-growing districts, and forms of it are found on oat, 

 barley, rye, and almost all grasses The losses from the form 

 on wheat, reported to the Board of Agriculture in 1892, vary 

 from nine to sixteen bushels per acre of crop. Rust-epidemics 

 have been the subject of special attention in Europe, more 

 particularly in Sweden, Germany, France and Austria. A rust 

 conference was formed in 1890 for Australasia, and still con- 

 tinues to meet. In the United States of America, the Depart- 

 ment of Agriculture sanctions the statement that " the damage 

 to wheat and oats from rust in this country probably exceeds 

 that caused by any other fungous or insect pest, and in some 

 localities is greater than that caused by all other enemies com- 

 bined " (Carleton, M. A., "Cereal Rusts of the United States," 

 U.S. Department of Agriculture, Bulletin 16, 1899). In India 

 and Japan, substantial losses are ascribed to this disease. 



The remedy for this epidemic is a difScult problem, and the 

 aim of recent research has been, in the first place, to obtain 

 a true conception of the fungus causing it. The facts leading 

 up to recent investigations may be briefly reviewed. It is an 

 old and deep-rooted belief amongst growers of wheat that the 

 rust of their crops is influenced by the neighbourhood of bar- 

 berry bushes. Evidence of this is seen in certain old enactments 

 enforcing destruction of the barberry ; for instance, that passed 

 by a parliament at Rouen in 1660, and others included in the 

 Province Law of Massachusetts (America) between 1738 and 

 1761. Sir Joseph Banks, in his paper (1805), holds the 

 same opinion. 



In 1841 Prof. J. S. Henslow {Journal of the Royal Agri- 

 cultural Society, vol. ii. 1841) suggested that the yellow summer 

 rust of wheat, and the black mildew which comes later, are 

 stages in the life of one and the same fungus. Passing over 

 many papers discussing these relationships, we come to one by 

 De Bary published in 1865 (" Untersuchungen tib. Uredinere." 

 Monatsber. d. Berlin Akad., 1865). From his experiments De 

 Bary concludes, that the yellow summer rust {Uredo linearis, 

 Persoon) on Gramineae, the black autumn rust {Puccinia 

 graininis, Persoon) also on Gramineae, and the rust on bar- 

 berry {Accidiutn berberidis, Persoon) with its associated 

 " spermogonia " stage, are phases in the life-history of the 

 same fungus, for which the name Puccinia graminis is retained. 

 In other words, that three (or four) recognised species of fungi 

 are one and the same. At the same time a new phenomenon 

 in the life of fungi was revealed, namely, that there existed 

 parasitic fungi which required two host-plants in order to 

 develop the forms of reproduction included in their life-cycle ; 

 this De Bary named meioecism or (as better known in Britain) 

 hetercecism. The life-history of Puccinia graminis, as defined 

 by De Bary, is given in all our text-books. Uredospores (see 

 Fig. i) are produced on wheat and other Gramineae throughout 

 the summer, and infect the same group of host-plants ; the 



