Oct. 9, 1879] 



NATURE 



557 



I 



period, but if it is short many revolutions must be 

 watched. These stars proceed more quickly from mini- 

 mum to maximum than from maximum to minimum, and 

 this is also the case with new stars. At last it is found 

 that the colour is most monochromatic nearest the mini- 

 mum. The brightness of the comparison stars is best 

 obtained from their comparison with the variable and 

 become therefore better known the more revolutions are 

 watched. The final discussion will sometimes show that 

 one or more of the comparison stars are variable them- 

 selves, for astronomers agree that there are many more 

 variable stars in the sky than those contained in the 

 catalogues. 



As to the physical explanation of these phenomena we 

 do not learn much from Argelander, who was one of the 

 last champions of the old school. It is even said about 

 him that he to the last stuck to Herschel's theory of the 

 structure of the sun in spite of this being opposed to New- 

 ton's axioms, and framed, according to the now obsolete 

 assumption, that erery heavenly body ought somehow to 

 furnish a comfortable abode for beings like ourselves. 

 We can only comprehend unknown things from what is 

 already known to us, and it is therefore rational to sup- 

 pose variable stars analogous to our sun, whose lustre 

 must vary with the extent of its spots. It is no doubt 

 reserved to the spectroscope to settle the question, mean- 

 time we can only keep in view Hind's important remark 

 that variable stars are often of a ruddy colour, and appear 

 surrounded by nebulosity at their minimum. W. D. 



COFFEE-LEAF DISEASE OF CEYLON AND 

 SOUTHERN INDIA 



I. ZJISTORICAL REMARKS.— -Dunng the last ten 

 ■* ■* years, the coffee plantations of Ceylon and Southern 

 India have had to contend with a disease which has 

 seriously affected their productiveness and entailed a heavy 

 loss upon the proprietors. This disease, Hcmikia vastatrix, 

 popularly known as the coffee-leaf disease, was first ob- 

 served in May, 1 869, on a few plants in Madulsima, a newly- 

 opened coffee district in the south-west of Ceylon, bordering 

 on the low country. In July following, two or three acres 

 were attacked, and from that time the disease has 

 gradually spread, till, in 1873 all, or nearly all, the estates 

 in the island were attacked by it. On the appearance of 

 the disease in 1869, the distinguished fungologist, the 

 Rev. M. J. Berkeley, determined its true character, and 

 described it in the Gardeiur' s Chronuleior 1869 (p. 1,157, 

 with v.'oodcut). It was found to be a fungus allied to the 

 moulds, and named HemiUia vastatrix, B. and Br. It 

 was subsequently described in the Journal oi the Linnean 

 Society ("Botany," vol. xiv. p. 93, pi. 3, Fig. 10), and a 

 short notice appeared in the Quarterly Journal of Micro- 

 scopical Science, 1873, pp. 79-81. In 1876 Dr. M. C. 

 Cooke described and figured the disease from Indian 

 specimens in the India Museum Report, 1876, pp. 4-6. 

 More recently the Rev. R. Abbay, who, during several 

 years residence in Ceylon, made this disease an object of 

 special study, gave a fuller description of it, with the 

 results of his observations upon the germination of the 

 spores and their growth under artificial cultivation, in the 

 Journal of the Linnean Society, 1878 ("Botany," vol. 

 xvu. pp. 173-184, pi. 13 and 14). 



In his first noiicc of the disease the Rev. M. J. Berkeley 

 speaks of it as a " minute fungus which has caused some 

 consternation amongst the coffee planters of Ceylon in 

 consequence of the rapid progress it seem; to be making 

 amongst the coffee plants." He further remarks : " It is 

 not only auite new, but with difficulty referable to any 

 recognised section of fungi. Indeed, it seems just inter- 

 mediate between true mould and Uredos, allied on the 

 one hand to Trichobasis, and on the other to Rhinotrichum. 

 Though the fungus is developed from the parenchyma of 



the leaf, there is not any covering to the little heaps, such 

 as is so obvious in Uredo and its immediate allies, while 

 the mode of attachment reminds one oi Rhinotrichum.'" 

 At that time no other form of Hemileia was known, and 

 it was supposed to stand alone as the only species, and 

 to be indigenous to Ceylon. Since then, another species 

 of Hemileia, viz., H. canthii, B. and Br., has been found 

 on a Ceylon jungle tree, Canthium campanitlatum^ and 

 lately Dr. Cooke appears to have met with a third species 

 from Southern Africa. 



Writing in 1874, Dr. Thwaites, the distinguished 

 Director of the Botanic Gardens, Ceylon, describes the 

 Hemeleia vastatrix as " a parasitic growth within thelcoffee 

 tree of a well-defined species of fungus, originated and 

 reproduced by means of spores, easily distinguished from 

 every other known fungus." " There can be no question," 

 he continues, "that this fungus is communicated from 

 coffee plant to coffee plant through the dissemination 

 of its spores, and that these may be conveyed by the 

 wind, or by streams of water, or by animals of any kind 

 moving from place to place." Though at first it was 

 believed that some elements of the fungus were present 

 " in the growing tissues of the coffee plant in a diffused 

 form," this view was afterwards abandoned, further micro- 

 scopical investigations having proved that the disease was 

 mainly external, and " that the coffee tree suffered rather 

 frorn exhaustion than from the poisoning of its juices." 

 During 1S73 and 1874 investigations of an important 

 character were carried on by Dr. Thwaites and the Rev. 

 R. Abbay, which led them to the conclusion that when 

 grown upon charcoal kept constantly moist, the orange- 

 coloured spores representing the fruit of the disease, gave 

 rise to filaments more or less branched. At the termina- 

 tion of the branches '^secondary spores appear to hare 

 been produced in the form of radiating necklace-shaped 

 strings of little spherical bodies of uniform size, closely 

 resembling the fructification of an Aspergillus." 



2. Effects produced.— The effects of the fungus upon 

 the coffee trees would seem to be the gradual loss of vital 

 energy caused by repeated destruction of the leaves. 

 The tree after the first attack of the disease, which is often 

 apparently the most severe, throws out fresh, healthy- look- 

 ing leaves, and exhibits for a certain period the appearance 

 of having perfectly recovered. These fresh leaves, how- 

 ever, after the expiration of a few months, exhibit the 

 characteristic spotting, and are sooner or later covered, on 

 the under side, by orange-coloured dust representing 

 the spores of the disease, and, as in the previous attack, 

 fall prematurely. These repeated attacks at length 

 seriously affect the heaUh of the tree, which, if old 

 and ill-cultivated, becomes of little or no value as a crop- 

 producer. 



The rapidity with which the disease was propagated 

 after its first appearance, may be realised from the fact 

 that although it was noticed only in one locality in May, 

 1869, it quickly spread to die neighbouring coffee-districts, 

 and especially among native coffee, till in 1873 it was 

 spoken of " as being found in nearly all, if not all, the 

 estates in the island." The disease appears to have 

 been noticed in India in 1869 and 1870, almost simul- 

 taneously with its appearance in Ceylon." In February, 

 1874, its presence was seriously felt in Tellicherry, and 

 it appears to have spread generally through the Wynaad 

 and Mysore districts, and its first effects were so severe 

 that it threatened to give a considerable check to coffee 

 enterprise in Southern India.' In 1876 the disease 

 appeared in Sumatra, and this year it has been found in 

 the plantations of Java and Bencoolen ; there can be little 

 doubt, therefore, that the Hemileia is destined to be a 

 wide-spreading and prevalent enemy in all coffee-pro- 

 ducing areas of the East Indies. 

 The effects of the leaf-disease upon the exportation of 



■ "Enum. Plant. Zeylan. Rubbcc.-c." p. 153. 

 " Report of Indiri Museum, M. C. Cooke, 1876. 

 3 Gardmcr't Chronicle, February, 1874. 



