194 



extraction of fibre. The first sign of it is the appearance of white 

 blotches which spread, then darken to a deep brown, bc;coming 

 sunken, and when quite dead the skin takes on a rather silvery 

 look; this change is followed by the breaking out of small black 

 pustules which are often in rather regular concentric rings. 



On cutting sections of the diseased parts of the Sisal plants it 

 can be seen that in the earlier period of the attack the bleaching 

 is due to the destruction of the chlorophyll-containing cells 

 under the epidermis, whereby cavities are formed leading to the 

 shrinkage of the dying epidermis onto the layer of fibre? below. 

 The whole afterwards becoming more and nvire disorganised, air 

 obtains access to the cavities; and this leads t) the silvery appear- 

 ance. In the final stage spores of a fungus are formed in the cavity 

 under the epidermis and escape through cracks in it. 



The attack is like that of the fungus Colletotrichum Agaves 

 which is described and figured in the Sixteenth Annual Report ot 

 the Missouri Botanic Garden, 1905, p. 153, plates 35-37, but the 

 destruction seems to spread more longitudinally down the leaf, and 

 under the microscope it is seen that the spores are not the spores of 

 a CoUetotrichunu but of a fungus of the allied genus Coryneiim. 



Coryucnm and Collctotrichinii both belong to the Melanconiales, 

 and as they are of the same habit, the treatment for one would seem 

 to be the treatment for the other. 



Colletotrichum Agaves is known to occur in India, and may be 

 attacked as recommended by Dr. Butler, in the Agricultural Journal 

 of India, i. p. 260, thus : — 



" Sisal Hemp Disease. A disease of cultivated Agaves, caused 



by the fungus Colletotrichum Agaves has been found in several 



parts of India, and has been the cause of alarm on Sisal estates. In 

 America it has not been known to attack Sisal ; but in India it often 

 does so. The older leaves are first attacked, sunken patche-; appear- 

 ing where the fungus has entered. These turn brown and dry up in 

 the centre, while they spread at the margin In the dried up parts, 

 spores are produced in little black clumps, which blow ab uit and in- 

 fect healthy leaves All diseased leaves should be cut and 



burnt as soon as the patches appear." 



In the Report of the Missouri Botanic Garden, it is recorded that 

 the garden authorities had succeeded in checking the spread of the 

 disease by such means ; but it is added that moisture predisposes 

 to the attack. Missouri with its dry climnte then has a great advan- 

 tage over this country where we cannot avoid the moisture. 



1. H. BURKILL. 



