The Supplement to the Tropical AgriculUirirt 



of disease half of the main roots were found to 

 be affected with this rot while the proportion 

 of the smaller roots rotted was much higher. In 

 milder cases only three or four main roots may- 

 be rotten while, even on the *ound roots, per- 

 haps fifty per cent of the rootlets will be dead. 

 The disease therefore manifests itself chiefly 

 through alterations produced in the leaves and 

 in the roots and it is necessary to ascertain in 

 which of these parts it has its original seat. In 

 the leaves the wilting and discolouration of the 

 leaflets are not induced by parasitic attack. The 

 leaf tissue simply gets pale and flaccid. 

 Even when this extends to the whole leaf trtere 

 is still no indication of any local parasite at 

 work. The condition is merely one of starvation 

 and drought. When the leaf ends die, no doubt 

 fungi appear, but fungi always fasten on any 

 dead plant tissue and an examination of those 

 found showed that they were common moulds 

 and harmless species, feeding on the dead tissues. 

 The minute plants known as fungi are as a 

 whole divided into classes according to their 

 food requirements. The larger class, the 

 saprophytes, live on dead organic matter, chiefly 



filant remains ; they car.not get their food from 

 iving tissues such as growing plants. The 

 smaller class, the jarasites, are on the contrary 

 able to attack and feed on living tissues, and 

 are the cause of a vast number of diseases of 

 plants. On the leaves of diseased palms no 

 parasite was commonly found such as would be 

 sufficient to account for their unhealthy con- 

 dition. Were one present we would expect to 

 find the first attack confined to one or several 

 small areas, whereas in fact a large number of 

 leaves may 



TURN YELLOW AND ALL THEIR LEAFLETS BEING 

 TO DROOP SIMULTANEOUSLY. 



In the roots matters are different. The root itself 

 consists of an outer layer of thick-walled cells 

 which forms a protective covering. Within this 

 thereis a zone of variable thickness, composed 

 of cells with moderately thick walls which be- 

 come larger, looser and have thinner walls as 

 they are further from the surface. This is 

 known as the cortex. Within the cortex, and 

 forming the central tough strand of the 

 root, is a body of mostly thick-walled cells 

 called the central cylinder. It is through the 

 latter that the vessels run which convey water 

 and food salts from the soil to the stem. La- 

 teral roots affected by the rot mentioned above 

 are invaded by a parasitic fungus, which enters 

 from the soil and develops the minute threads 

 of which its body is composed in and between 

 the cells of the cortex. When a root becomes 

 invaded by this parasite the cortical cells are 

 killed as soon as a thread of the fungus reaches 

 them. They quickly turn brown and collapse. 

 This is especially marked in the large thin- 

 walled cells of the inner layers. At a later stage 

 the whole root appears blackened and shrunken 

 as a result of the death of a large number of its 

 cells ; it can evidently no longer perform its 

 work of taking in food, and decomposition 

 rapidly sets in. The threads of the parasite 

 are of two kinds. The older ones are deep 

 brown and comparatively large. From them 

 arise finer colourless bran'ches. All are divided 

 into segments by transverse walls. In older 

 stages masses of these brown threads be- 



come crowded together and divide fre- 

 quently, so that a brown patch of fungus 

 tissue is formed. In this, at a still later 

 stage, spore capsules are developed under the 

 rind and these burst out to open on the surface 

 of the root and discharge spores. 



THE SPOKES ARE RATHER LARGE, EGG-SHAPED 

 BODIES, 



colourless and single when young but divided 

 into two cells and deep brown when older. 

 It is a species of the genus Botryodiplodia, 

 of which several parasitic members are known. 

 Quite recently Mr. F A Stockdale, Myco- 

 logist to the Imperial Department of Agri- 

 culture, West Indies, has described a similar 

 and perhaps identical species as the cause of 

 a serious coconut disease in Trinidad. The 

 symptoms of this disease are on the whole 

 similar to those described above and it 

 appears to be possible that both are really 

 the same. There is no absolute proof that the 

 Botryodiplodia is the cause of the disease either 

 in Travancore or in Trinidad. It is not even cer- 

 tain that the two are identical, as the scientific 

 description of the latter has not been published, 

 ho far as can be gathered from Mr. Stockdale's 

 report the spores of his fungus were not found 

 actually on coconut roots, but only on the leaf 

 potioles, though he attributes the death of the 

 roots to a fungus found in them and apparently 

 agreeing with that on the petioles. In Travan- 

 core the Botryodiplodia was only found on roots 

 but was obtained on diseased roots of areca as 

 well as coconut palms. Spores were not found 

 on roots actually in the soil but developed on 

 diseased roots after these had been dug up and 

 kept for some time. Only the early stages of 

 formation of the spore capsules were found 

 in freshly dug roots. The brown threads within 

 the roots were found in these cases to communi- 

 cate with the spore capMiles, both immature 

 and ripe and there is no doubt that the threads 

 of diseased roots belong to the Botryodiplodia. 

 Scientific proof that this fungus is the cause 

 of the disease can only be obtained by inocu- 

 lating the roots of healthy palms with a culture 

 of the fungus and 



THEREBY PRODUCING THE DISEASE. 



This has not been possible in the time at my 

 disposal and would require facilities for isolating 

 and growing the fungus which were not avail- 

 able in Travancore. All that can therefore be 

 safely said is that the roots of diseased palms 

 are rotted by the attacks of a parastic fungus ; 

 that this fungus appears to be a B dryodip'odia ; 

 and that probably the root rot caused by it is 

 sufficient to produce the disease at present 

 ravaging the coconut gardens. The effects of such 

 a parasitic attack on the roots will be at once 

 clear if we consider the work which healthy 

 roots have to perform. For healthy growth a 

 tree requires a supply of carbou dioxido and 

 oxygen from the air, and water with dissolved 

 salts from the soil. The latter are useless to the 

 plant u itil they are carried up to the leaves, 

 where they become transformed into food. For 

 this purpose a steady flow of water containing 

 the salts in solution must be maintained 

 between the roots and leaves. The surplus 

 water at the top is got rid of by "transpiration " 

 or evaporation into the air. Besides its use n 



