20 



and acting sporadically on the more 

 superficial cells of the cortical layer of 

 the plant and on their contents. 



No micro-chemical action of this character 

 has, however, been determined, and it 

 can, therefore, be conjectured only — if 

 it, indeed, actually takes place — in what 

 it consists. 



In this connection it may be remarked that 

 in the Prickly-pear a singular feature is 

 exhibited, consisting in the presence of 

 a layer of cells, intervening between the 

 chlorophyl containing palisade cells and 

 the epidermis, each of which contains a 

 large sphcerolith of oxalate of lime, and 

 this is denotive of the fact that duriug 

 the growth of the plant a large amount 

 of oxalic acid is formed, probably in 

 connection with the special metabolism 

 involved. 



Could we conceive that under exceptional 

 circumstances the reduction of this 

 oxalic acid takes place to form poisonous 

 bodies — e.g., glycollic or glycoxylic acids 

 that are created in the course of this 

 process prior to its being rendered inert 

 through union with lime — such action 

 would account for the figure that charac- 

 terises the initial changes •when first 

 apparent — that of a drop of fluid 

 flattened out. However, as I am assured, 

 such action as is referred to is unknown 

 to the physiology of plant-life. 



Some attentioii has been given to the same 

 disease by the Imperial Mycologist, Dr. E. J. 

 Butler, who kindly placed the following note at 

 the disposal of the Commission, which, though 

 inconclusive, is of much interest: — 



" Early in 1904 I received specimens of 

 Prickly-pear* from the Conservator of 

 Forests, Central Circle, Madras. 



The Conservator stated that they were af- 

 fected by a disease which he had traced 

 over a stretch of country 150 miles long, 

 and that, in the drier soils and where 

 fully exposed to sunlight, it certainly 

 resulted in the death of one-third to 

 one-half of the plants. His description 

 was that small spots appeared on the 

 " leaves," around which developed cir- 

 cular brown patches; the " leaf " be- 

 came yellow, wax-like, and translucent, 

 and then the lower stems turned brown 

 and decayed. The blossoms were few, 

 and the flowers and fruit were un- 

 healthy and rotten. When growing in 

 shade, the plants did not succumb so 

 : readily, the " leaves " not becoming 



translucent, and the main stems not de- 

 caying so completely, and reviving and 

 resuming growth when moistened. 



Later information from the same source in- 

 dicated that the area infected included 

 part of Salem, Trichinopoly, North 



*The species is O. dUknii. Dr. Butler showed 

 P^a° ^ * *™^ ^'^"^^ (diseased) which he had at 



Arcot, and Cuddapah districtt?, It was 

 stated to have been known in Salem 

 since 1896. 



In October, 1904, I visited Manaparai, a 

 little south of Trichinopoly, to examine 

 the disease on the spot. I also carried 

 out more detailed examinations, and 

 tried to reproduce the disease in my 

 laboratory at Dehra Dun. 



The results of this work were to throw 

 doubt on the condition observed by the 

 Conservator being due to a definite dis- 

 ease or being capable of entirely killing 

 the plant. 



Many of the spots were found to be duo to 

 insect punctures, through which semi- 

 parasitic fungi and bacteria entered the 

 " leaf " tissues and sometimes set up a 

 rot. In severe eases the rotting ap- 

 peared to spread over the whole plant, 

 except the root stock; and in such cases 

 bacteria appeared to be the cause of the 

 rotting. The root stock, however, was 

 always found uninjured and capable of 

 throwing out new stems. Even half- 

 dead ' ' leaves, ' ' which had broken away 

 from the rest of the plant, were found 

 rooting freely and sending out new 

 sound shoots. In several cases seen the 

 effect of the ' ' disease ' ' was actually to 

 multiply the pest by breaking up a 

 single plant into a number of indepen- 

 dent units. 



My conclusions were that the constant re- 

 newal of growth from plants wholly or 

 partially rotted in their above-ground 

 parts put it out of the question that any 

 permanent lessening of the pest could 

 be hoped for from the disease. 



In this opinion I was supported by the na- 

 tives whom I questioned, and by the 

 Forest Sanger at Manaparai, all hold- 

 ing that the rot was only temporary and 

 that the plant iiltimately revived. ' ' 



The Principal of the Agricultural College 

 and Research Institute, Coimbatore, informed the 

 Commission that an instance of a so-called disease 

 was afforded by an occurrence at the Saltpans of 

 Chingelput, a place situated a little to the south 

 of iladras ; and that in this case it has a peculiar 

 economic bearing, since the occasion of its being 

 noted was the inability of the local manager to 

 maintain intact a hedge of Prickly-pear that sur- 

 rounded the factory buildings there. Mr. Cecil 

 Wood, to whom tho matter had been thus re- 

 ferred, inclined— as he stated— to the opinion 

 tliat it was merely a ease of the action of unsuit- 

 able soil conditions, arising from an undue pro- 

 portion of saline material being present. A super- 

 ficial examination of a specimen, derived from an 

 affected plant that he exhibited, was not in- 

 consistent with this explanation. However, he 

 was having this minutely examined by a mycolo- 

 gist on the staff of his department, since miero- 

 fungi were to be noted on the dead tissue. It is 

 uncertain whether the diseases mentioned by 

 Lieutenant-Colonel King, as ocvarring in 1895 

 m the Chingelput also, be identlv.ll with the one 

 now under review or be a distinct affection. 



