724 Journal of Agricultural Research vol. xx, No. 9 



it in the genus Colletotrichum. It was first collected in America in 

 1886 by Dr. Martin from Green Cove Springs, Fla., and was first reported 

 by L. M. Underwood (8) in 1891. However, the disease was not found 

 in California until some years later. It was reported by Essig (4) in 

 1909 from the Limoneira Ranch at Santa Paula, where it was causing 

 considerable damage to lemon trees. 



In 1904, Prof. P. H. Rolfs (5) gave a very good description of the 

 fungus as it occurred on various citrus trees and fruits in Florida. He 

 says (5, p. 20) that the — 



diseases . . . manifest themselves as wither- tip on orange, pomelo, and lemon twigs; 

 as leaf -spot on the leaves of the various citrous species; as anthracnose on lime blos- 

 soms, recently set limes, lime twigs, and lemon twigs; as lemon-spot on ripe lemons 

 and as canker of limes. 



The following description is given by Prof. P. H. Rolfs: 



Acervuli located on the surface of the leaf, twig or fruit; 90-270 n in diameter, 

 erumpent, superficial. Shape various, not uniform, occurring on either surface of 

 citrus leaves; disposed irregularly or in more or less concentric lines; pale to dark 

 colored. On tender lime twigs, tender lemon twigs, lemon fruits and lime fruits, pale 

 colored, dull red in masses, confluent. Epidermis breaks irregularly. Setae fuligi- 

 nous, ranging in length from 60-160 /x, frequently once or twice septate, disposed at 

 margin of acervuli. Frequently absent, and on tender lime twigs, tender lemon 

 twigs, lemon fruits and lime fruits usually absent. 



Conidia broadly oval or oblong, 10-16 m by 5-7 n, hyaline; size variable in same 

 acervulus, usually with one or two oil drops. Developing from a well-defined stroma; 

 basidia, 3-18 m- In moist chambers the conidia stream from the break in the epi- 

 dermis. Intrabasidial setae, variable 8-30^ by 3-6/i, cylindrical or sometimes en- 

 larged at distal end; hyaline. 



In 1 91 2 Clausen (/) described the fungus causing wither-tip of the lime, 

 Citrus medica, as Glocosporium limetticolum. He believes that Rolfs had 

 confused two forms and described them as one. Clausen uses the ab- 

 sence of setae as a distinguishing character from Colletotrichum 

 glocosporioides. It is the opinion of Stoneman (7), Edgerton (2), and 

 Shear and Wood (6) that the setae are variable as to presence or absence 

 and that they are not reliable morphological characters to use in separat- 

 ing genera. I have found them in some of my cultures of Colletotrichum 

 glocosporioides, while in other cultures they were absent. Another char- 

 acter he uses is the lack of a coarsely granular plasma filling the spores. I 

 have found several strains of this fungus which are considered to be 

 Colletotrichum gloeosporioides, whose spores are not filled with a coarse 

 granular plasma but appear at first to be homogeneous. Clausen also 

 uses growth characteristics as a means to identify the two strains. 

 Some of my strains had the same growth characteristics as the strain 

 which was obtained from Clausen — that is, a white mycelium and 

 abundant spore production. 



Shear and Wood (6) in their bulletin on the genus Glomerella, have 

 brought together strains from various hosts and included them in one 



