129 



merely geographical varieties of Pestalozzia palmarum Cke., and 

 not distinct species. 



27. During the short time that was given to the investigation 

 of this disease, evidence could not be obtained on the time it takes 

 from first infection by germination of a spore to the production of 

 a yellow spot on the leaf nor on the time it takes for spores to be 

 produced ; but the following information on this point has been 

 obtained during the work of Bernard on a similar disease in 

 Java : — 



'Two very vigorous coco-nuts situated near a diseased 



plantation were isolated and in the crown of one was 



placed a bunch of badly diseased leaves. After two 



months, (this is the period of time that is generally 



considered to be the period of ' incubation* of the disease 



i.e. the time which intervenes between the moment that 



infection takes place and that when the first exterior 



manifestations of the disease appear) this tree showed 



the characteristic spots upon its leaves ; spots which grew 



and caused three months later (i.e. five months after 



infection) the death of the tree. The adjoining tree, 



which was not infected, remained healthy and vigorous.' 



There can, therefore, be no doubt as to the cause of the disease 



or to the ease with which it can spread, for this parasite, as seen 



by the above experiment, is the primary cause of the disease 



and is not a secondary appearance on plants in bad condition. 



It would appear, however, that the leaf, after succumbing to the 

 numerous drains upon its resources, falls to the ground before the 

 mycelium has attained the possible limits of its development ; 

 for if a leaf that has fallen into a dry place be placed into a 

 moist chamber, a multitude of pustules bearing conidia will be 

 produced within 48 hours, while, if a leaf that has fallen in a 

 damp place, where it is shaded from the effects of the sun, be 

 examined, large numbers of spores can be seen to be given off, 

 thus showing that the mycelium is capable of further growth after 

 the leaflet has fallen to the ground. 



28. Evidence on the cause of the disease was gathered from 

 planters of coco-nuts, but, as in the root diseases the general 

 opinion was that it was due to the weakness of the plants, 

 produced by setting immature nuts, or to improper soil conditions. 

 It is impossible to believe that a large portion of an estate in 

 the Mayaro district or isolated patches in the Icacos district would 

 be planted by immature nuts alone, for the disease does not 

 appear upon a single tree here and there. As to improper soil 

 conditions, it is generally held that favourable conditions of soil 

 are necessary for the growth of strong, vigorous, healthy plants, 

 and therefore every effort should be made on the part of the 

 planter to understand the different soil conditions of his estate 

 and to assist nature whenever possible. This is the most 

 perplexing question with which the planter has to contend, 

 requiring judgment that can be gained only by many years of 

 practical experience. 



