DISEASESiCAUSED BY FUNGI 23 



falcatum produces the red rot of the sugar-cane stem and a red 

 stripe affection on the leaves and leaf-sheaths ; nearly allied 

 species occur on sorghum and other grasses. The citrus anth- 

 racnose {Col. glceosporioides), which under some conditions is 

 reported to produce on Citrus species in general effects similar 

 to those of the special anthracnose of the lime, is not known to be 

 of much account in the Lesser Antilles. The cotton anthracnose 

 Glomerella (Coll.) gossypii appears also to be responsible for much 

 less damage than is reported from it in the United States. 



For the control of anthracnoses it is desirable, in the first 

 place, to secure clean seed. Adhering spores can be dealt with 

 by the methods elsewhere described, but in some cases the 

 cotyledons are infected while the seed is still on the parent 

 plant. Hot water treatment has been suggested in the case of 

 infected cotton-seed, but with what ultimate results is not 

 known. 



For tree crops such as limes and mangoes the only remedy 

 is spraying, and this is the measure adopted for anthracnose in 

 general where the value of the crop warrants the outlay. The 

 control of the destructive epidemic of red rot on sugar-cane in 

 the West Indies was secured by the use of seedling varieties, 

 some of which have proved to be highly resistant, and others 

 apparently immune. Varieties of beans (Phaseolus) resistant to 

 the bean anthracnose fungus have been found, and the character 

 has been transferred to other types by crossing. Various strains 

 of this parasite have been shown to possess differential powers 

 of infesting particular varieties of the host. 



On the other hand, many of the reputed species of 

 Gloeosporium and Colletotrichum have been shown by infections 

 from pure cultures to have a very wide range of possible hosts. 



The Fusanums. 



The genus Fusarium includes many purely saprophytic 

 species and a considerable number of vey destructive plant 

 parasites. The latter are tjrpically confined to one host plant, 

 frequently even to the narrower limits of particular varieties 

 or strains, but are capable of living indefinitely as saprophytes, 

 very often in the soil. 



The species are very similar in morphological characters, 

 and for that reason, and because of the abundance of saprophytic 

 species likely to be confused with the parasites, have been 

 exceedingly dif&cult to identify. Of recent years the use of 

 standard culture media and of biometric methods in the com- 

 parison of species has removed much uncertainty and laid the 

 foundations of an exact knowledge which is much to be desired 

 with other genera. 



The most important section of the genus is the group of 

 species, similar in biological and morphological characters, 

 which function as vascular parasites, and by blocking or destroy- 



