It is generally considered that an excessive water supply, due 

 to heavy soil or poor drainage, is very harmful. Such a condition 

 is doubtless beneficial to the growth of many injurious fungi and 

 there is a decrease in yield through loss of roots by disease or drown- 

 ing (suffocation). Observations, made in connection with the mottling 

 disease, have indicated that cane suffers more readily from a lack of 

 water than from an over abundance. 



DROUTH. 



Tliis is undoubtedly the most important of the various factors 

 considered under the general heading. Large sections of the Island 

 are so habitually dry that irrigation is absolutelj^ necessary, and there 

 are other important districts which suffer from periods of drouth of 

 greater or less length at various seasons of the year. The influence 

 of lack of sufficient water has been readily noted in those places where 

 irrigation has been applied to some fields only. It often spells the 

 difference between a crop and no crop. 



One very important effect credited to lack of water is increase 

 of root disease. There is undeniably an increase in the amount of 

 fungTis present, and it is not uncommon to find whole fields of 

 stunted, yellow cane, apparently ruined by root disease. The exact 

 relation of drouth and the fungi found in connection with the roots 

 and the stalks of the cane is debatable. 



It seems altogether probable that the most trying situation for 

 cane is a succession of excessive rains and long drouths, a state of 

 affairs often existing over large sections of Porto Rico. 



ABNORMALITIES. 



In Java the various abnormalities of the cane plant have been 

 considered at great length (58). Many of the types reported for 

 that Island occur in Porto Rico, but in isolated cases so that no sig- 

 nificance is attached to tliem in the patliological work. 



Canes are quite commonly found with buds or eyes missing from 

 some of the nodes, or sometimes with two or more eyes at a node. 

 Germination of the eyes in situ often with the production of lengthy 

 shoots is common, being quite characteristic of certain varieties. It 

 also occurs at times in connection with stalk-borer or other injuries. 



There have occurred types of growth resembling those described 

 for "sereh," the short grass-like habit for instance, and the produc- 

 tion of adventitious roots along the stalk, but without other symptoms 

 being present. Such cases have occurred in connection with root 

 disease or insect injury. 



234 



