Plant Sanitation. 



240 



[September, 1909. 



fungus is extremely common on all dead 

 Hevea, no matter what the cause of 

 death was, and it is therefore very diffi- 

 cult to determine when it is parasitic 

 and when it is merely saprophytic. It 

 does not appear to be a very active 

 parasite. It undoubtedly kills off stumps 

 just after they have been planted out, 

 and it has been found to kill Castilloa 

 which had been damaged by fire. But 

 in the majority of cases it can only 

 attack the trees after some part has 

 been killed. It grows in abundance on 

 Hevea logs in the laboratory, though 

 these may have been quite healthy 

 when cut. Trees attacked by "die back" 

 should be pruned below the diseased 

 parts ; and the latter should be burnt. 

 In view of the fact that Botryodiplodia 

 will grow on any dead Hevea tissue, all 

 dead brauches ought to be periodically 

 removed and burnt; there is no doubt 

 that this will have to become a regular 

 practice in Hevea cultivation. Branches 

 die from many causes apart from fungus 

 diseases, e.g., wind, over-tapping, shade, 

 etc., and if these are left on the tree 

 they afford a starting point for fungi 

 which could net otherwise attack it. 



It is hoped to issue circulars on Brown 

 Root Disease, Die back, and Botryodip- 

 lodia, shortly. 



Botryodiplodia elasticce affords another 

 instance of the multiplication of names 

 which results from the transmission of 

 specimens of tropical diseases to Europe. 

 Species of Diplodia occur everywhere in 

 the Tropics, on all kinds of dead plants, 

 but the majority of them are merely 

 saprophytic, i.e., they grow only on 

 dead tissues. If a Diplodia occurs in 

 masses, it is known as Botryodiplodia, 

 and if the masses are surrounded by 

 loose hypha?, it is known as Lasiodip- 

 lodia. But, unfortunately, these appa- 

 rent distinctions breakdown in practice, 

 for the same species may exhibit all 

 three forms. In that case it usually gets 

 three different names, according to the 

 form which each describer happens to 

 have. Botryodiplodia is a convenient 

 name for those species which may some- 

 times grow in masses and sometimes 

 singly, and distinguishes them from 

 those species which always grow singly, 

 but Lasiodiplodia is a purely herbarium 

 distinction for which we have no use in 

 practice. 



The best known parasitic Diplodia is 

 Diplodia cacaoicola, which, as its name 

 indicates, grows on Cacao. Botryodip- 

 lodia elastics is also semi-parasitic on 

 Hevea and Castilloa. Another Botryodi- 

 plodia causes a root disease of tea, and 

 yet another a root disease of the Coco- 

 nut palm. Now, the Diplodia on Cacao 



{Diplodia cacaoicola) was sent to Ger" 

 many, and was unnecessarily renamed 

 there Lasiodiplodia nigra. More re- 

 cently, a consignment of Hevea stumps 

 was sent from Ceylon to Hamburg, and 

 as some of them died in transit they 

 developed Botryodiplodia elastics, but 

 the fungus was, in this case also, 

 assigned to Lasiodiplodia nigra. We 

 may expect to hear, therefore, of a new 

 disease of Hevea under the latter name, 

 which is really only our old, well-known 

 fungus. But a much more serious ques- 

 tion than the mere nomenclature is in- 

 volved in this bestowal of the name of 

 the West Indian fungus on the Ceylon 

 species, for it has been thereby assumed 

 that the fungus which attacks Cacao is 

 the same species as that which attacks 

 Hevea. This is a most important point 

 which, if correct, will have to be taken 

 into consideration by those who estab- 

 lish mixed cultivations. But while 

 it may be admitted that the diplodias 

 on cacao, Hevea, tea, and coconut 

 show practically no difference in 

 structure, this is scarcely sufficient to 

 warrant the assumption that they are 

 all the same species. The structural 

 characters of a diplodia are very simple, 

 and there is little room for variation. 

 Under these circumstances, it is neces- 

 sary to prove the identity of the fungi 

 by showing that the species, say on 

 cacao, can be made to grow on the other 

 plants. Until this has been done, the 

 question of their identity must remain 

 uusettled. The point was noted in the 

 Report of the Mycologist for 1908, but 

 since the investigation of the subject 

 would occupy several months, it has not 

 yet been found possible to undertake it. 



Opinions with regard to the distances 

 at which Hevea should be planted have 

 now come round to the view which had 

 to be fought for in 1906. It is no longer 

 necessary to contend with the idea that 

 Hevea may be planted eight feet by 

 eight; and it is being recognised that 

 the minimum advocated three years ago 

 is not " wide planting," if the plantation 

 has been established as a permanent 

 investment. But, as I was the first to 

 oppose close planting in Ceylon, I have 

 been asked on several occasions why, if 

 Castilloa can be planted about eight 

 hundred to the acre, the same cannot 

 be done in the case of Hevea. The 

 answer is, of course, that the trees are 

 of different habit, that is, they have a 

 crown of a different shape. Dr. Ohlson 

 Seffer, who is the chief authority on 

 Castilloa cultivation, described the 

 Mexican methods when hi visited Ceylon 

 some years ago. In the course of con- 

 versation, he stated that when the trees 



