494 



NA TURE 



[September 13, 1906 



.admission by the root-hairs, though he thought the 

 parasite was a myceloid fungus, whereas it has since 

 •been proved to be a bacterium. The whole subject 

 was admirably resumed by him in an article con- 

 tained in vol. i. of the Annals of Bo/any (1887-8), of 

 which periodical he was one of the founders. The 

 same volume opens with a paper by him and Mr. T. 

 Dunlop on the histology and physiology of the fruits 

 and seeds of Rhamnus, perhaps one of 'the best of his 

 researches, in which it is shown that the yellow pig- 

 ment (rhamnin), obtained from the fruits for dveing 

 purposes, is formed by the decomposition of the 

 glucoside (xanthorhamnin) contained in the pericarp 

 by a ferment e.xisting principally in the testa of the 

 ■seed. In the second volume of the Annals (1888-9) 

 there is an elaborate paper, "A Lily-disease," the 

 chief point of interest being the discovery that the 

 fungus (Botrytis) penetrates "the cell-walls of the host 

 "by means of a ferment (since termed cvfase) secreted 

 at the tips of the hypha. Ward's views' on parasitism 

 were further developed in his paper " On some Re- 

 lations between Host and Parasite in certain Epidemic 

 Diseases of Plants" (Proc. Roy. Soc, vol. xlvii., 

 1890), which gained the honour' of selection as the 

 Croonian Lecture for that year. Passing over with 

 mere mention the papers on Craterostigma (Trans. 

 Linn. Soc, 1890) and on the Ginger-beer Plant (Phil. 

 Trans., 1892), I come to his most laborious achieve- 

 ment, a series of reports on the bacteriology of the 

 Thames, presented, in conjunction with Prof. Percy 

 Frankland, F.R.S., to the Water Research Committee 

 of the Royal Society in the years 1893-6. It is diffi- 

 cult to form any adequate co'nception of the unfailing 

 assiduity necessary to the working out, as Ward did, 

 of thelife-histories of the no less than eighty diiTerent 

 ■bacterial organisms that he found in the river, nor is 

 It possible here to give an account of these voluminous 

 documents, a risumi of which, so far as his share 

 of the work is concerned, was given by him in the 

 fifth report (Proc. Roy. Soc, vol. Ixi., 1897). He had 

 proved his fitness for this difficult task by his paper 

 " On the Characters or Marks employed for Classify- 

 mg the Schizomycetes " in the Annals of Botany, 

 vol. yi., 1892, and the accomplishing of it gave rise to 

 such interesting parerga as the papers " On the Action 

 of Light on Bacteria " (Phil. Trans., 1895), " A Violet 

 Bacillus from the Thames," and "Some Thames 

 Bacteria " (Ann. Bot., xii., 1898). The first of these 

 papers is of considerable importance in that the 

 bactericidal effect of light, whether of the sun or of 

 the electric arc, is conclusively demonstrated, and is 

 shown to be confined to the more highly refrangible 

 rays of the spectrum. 



Ward_ was a regular attendant at the meetings of 

 the British Association for the Advancement of 

 Science, and was president of the botanical section 

 at the meeting in Toronto in 1897. His address on 

 that occasion dealt with a subject that was always in 

 bi> mind, the economic significance of the fungi, of 

 which he gave a characteristically exhaustive account. 

 In fact, all his subsequent work was the expression 

 ■of this idea. Thus in 1S98 (Phil. Trans.) he published 

 an investigation of Stereum hirsutum, the fungus 

 that attacks the wood of the oak, having succeeded, 

 ■by means of pure cultures, in tracing its life-history 

 from the spore to the fructification, "and he did the 

 same for Onygena equina, the horn-destroying 

 fungus (Phil. Trans., 1899). He then entered upon 

 what was destined to be his last line of research, the 

 investigation of the Uredinesor Rusts, with an energy 

 that was remarkable even for him ; but it was not 

 until 1902 that the publication of the results began, 

 ^o long and so numerous were the experiments from 

 which they were drawn. The first paper on the sub- 

 NO. 1924, VOL. 74] 



ject was read before the Cambridge Philosophical 

 Society in January, 1902 (Proc, vol. xi.), treating 

 of the physiological races of these fungi, with special 

 reference to the Brown Rust of the Brome-grasses. 

 Having shown that certain species of Bromes can 

 only be attacked successfully by certain forms or 

 breeds of the Rust, he arrived at the striking con- 

 clusion that " the capacity for infection, or for resist- 

 ance to infection, is independent of the anatomical 

 structure of the leaf (of the Grass), and must depend 

 upon some other internal factor or factors in the 

 plant." Two papers published later on in the year 

 (Proc. Roy. Soc, vols. Ixix. and Ixxi.) discuss the 

 question, with an answer in the negative, as to 

 whether or not susceptibility to infection depends 

 upon the nutritive conditions offered by the host to 

 the parasite, the foregoing conclusion being re- 

 asserted thus : — " All the evidence points to the exist- 

 ence, in the cells of the fungus, of enzj'mes or toxins, 

 or both, and in the cells of the host-plant of anti- 

 toxins or similar substances, as the decisive factors 

 in infection or immunity, although I have as yet failed 

 to isolate any such bodies." In the meantime yet 

 another paper had appeared in the Annals of Botany 

 (vol. xvi., June, 1902) confirming his previously ex- 

 pressed conviction that differences in details of 

 anatomical structure do not afford any explanation of 

 the relations between the Bromes and their Rusts. 

 His last paper on this subject is that dealing with 

 the adaptive parasitism of the Brown Rust (Annales 

 Mycologici, vol. i., 1903), in which he developed the 

 interesting idea of the existence of what he termed 

 "bridging species." The idea is briefly this, that 

 although it is generally true that the adapted races 

 of the parasitic fungus are restricted to groups of 

 closely allied host-species, there do occur host-species 

 which serve as intermediaries in the passage of the 

 parasite from members of one section of the host- 

 genus to those of another section. 



Incidentally, a controversy arose between Ward and 

 Prof. Eriksson, of Stockholm, with reference to the 

 " mycoplasm-theory " of the latter. In order to 

 account for the occurrence of sudden and widespread 

 epidemics of Rust, Eriksson had assumed the persist- 

 ence in a dormant state, within the tissues of the 

 host-plants, of a combination of the protoplasm of the 

 fungal hyph» with that of the host, which he had 

 described and figured and had called "mycoplasm." 

 .'\s stated in his paper on the question (Histology of 

 Uredo dispena, &c., Phil. Trans., Ser. B, vol. cxcvi., 

 1903), Ward was unable to confirm Eriksson's observ- 

 ations, and regarded his assumption as unnecessary. 

 One of the most interesting discussions in Section K 

 during the Cambridge meeting of the British Associ- 

 ation, 1904, was that in which the pros and cons of 

 this theory were urged by the two protagonists. 

 Their views were subsequently published, side by 

 side, in the Annals of Botany (vol. xix., January, 



1905)- 



At this point the record of his work as an in- 

 vestigator abruptly ends, when great things might 

 still have been anticipated, and it might well be 

 deemed sufficient to have occupied all the time and 

 energy at his disposal. However, this is far from 

 being the case. Besides writing all these papers, 

 many of them illustrated by elaborate drawings — for 

 Ward was an excellent draughtsman — as well as 

 others necessarily omitted here, he produced several 

 books : — a translation of Sachs's " Physiology of 

 Plants," 1884; "Timber and some of its Diseases," 

 i88q; "The Oak," 1892; an edition of Laslett's 

 "Timber and Timber-trees," 1894; "Diseases of 

 Plants," 1889; "Grasses," 190 1 ; "Disease in 

 Plants," 190 r ; "Trees," a considerable work, of 



