146 CARL DOWNEY LA RUE 



study the concept of P. Guepini employed is that given in a preliminary 

 study of the strains of the species by LARus and BARTLETT (1922). 



In this investigation the authors found that from thirty-five isolations 

 of Pestalozzia from the Para rubber tree, the cocoanut palm, the African 

 oil palm, the betel palm, and the tea plant, at least fourteen strains, 

 distinct in regard to morphological characters, could be distinguished. 

 More minute morphological studies would in all probability have resulted 

 in the division of some of these strains into smaller distinct groups. Cross 

 inoculations might possibly have revealed variations in regard to hosts 

 infected, and physiological studies would almost certainly have shown that 

 some isolations differ physiologically from others in the same morpho- 

 logical group. The large number of forms found within the comparatively 

 limited territory on the East Coast of Sumatra, from which the cultures 

 were secured suggests that an equally large number of strains might be 

 found in other regions, many of them doubtless distinguishable from those 

 already studied. The formation of at least one new strain by mutation 

 during the period covered by the present investigation of the effect of 

 selection leads to the belief that other strains are now being formed in 

 nature and that P. Guepini is a species in what may be called a plastic 

 condition. In this respect it is comparable to the organisms studied by 

 other recent workers who have sought to find a clue to the process by 

 which evolution proceeds. 



Only the spores' of the fungus were studied minutely by LARUE and 

 BARTLETT (1922) in the investigation of variability in P. Guepini men- 

 tioned above. The vegetative characters and growth habits also show 

 considerable variation but these are much more limited in range and more 

 difficult to measure than the quantitative characters of the spores, and 

 therefore were not utilized. For selection studies also, the spore characters 

 were chosen as most suitable though other characters might* have given 

 equally satisfactory results had they been more easily measured. 



The spindle-shaped spores of Pestalozzia Guepini are composed of five 

 cells of which the three central ones are smoky or black at maturity, while 

 the other two are hyaline. The distal hyaline conical cell normally bears 

 at its tip three slender, unjointed, hyaline appendages which diverge so 

 that their tips are widely separated. Spores are occasionally found which 

 contain three or four cells, and others which bear two appendages or 

 even only one, but these are apparently aberrant forms. Thus far no 

 strain has been found which is constant for any of these peculiarities, 

 and in the cases where the aberrant spores have been tested, they have 

 produced normal progeny. 



