524 BOTANICAL GAZETTE [june 



temperature data for the Yuma date orchard covering the two 

 years. Table I suggests that the greater prevalence of the fungi 

 concerned in the rot of the date fruit in 191 7 was possibly due to 

 the more favorable conditions of moisture and temperature during 

 April, May, and June, while flowering and fruit setting were in 

 progress. From observations it appears probable that infection 

 occurs at that time. The spring and summer of 19 17 had not 

 only an excess of moisture over the same period of 191 8, but were 

 also cooler, so that this additional moisture was more effective. 



Symptoms. — The fruits showed two main symptoms. Some 

 were flecked with rusty brown spots from the size of a pinhead to 

 areas almost covering one side of the fruit (fig. 4) ; others showed 

 soft spots varying in size and partly translucent, as though soaked 

 with water or oil (fig. 5). The brown spots gradually increased in 

 size, often coalescing, forming a dark chocolate margined area 

 oval in outline, with depressed, light cream or grayish centers on 

 which clusters of spores finally appeared in pustules (fig. 4, third 

 fruit, third row). The soft spots also enlarged to a similar 

 extent, giving an appearance of rot. In both cases the ruptured 

 epidermis allowed excessive water loss, resulting in the final 

 mummy stage. Mummified fruits sometimes remained for a time 

 in situ, but sooner or later fell to the ground (figs, i and 3). 

 The exposed sweet pulp, in the early stages of the soft spots, 

 attracted swarms of small flies and other insects which hovered 

 in and around the fruit clusters, and probably aided materially in 

 carrying the infection. 



Examination of the trees revealed numerous brown spots on 

 petioles and ribs of leaves, which also extended down the rhachi 

 of fruit clusters. This suggested a relation between fruit spot and 

 leaf spot, which appears to be confirmed by the laboratory experi- 

 ments so far completed. In the Tempe date orchard palms three 

 years old already showed the brown spots on the leaf bases. 



Laboratory studies.— Cultures have been made from the 

 spots on leaves, rhachi, and fruits collected in both orchards. The 

 medium used was date agar, prepared according to the method 

 described by Shear and Stevens 2 for prune agar by substituting 



3 Shear, C. S., and Stevens, N. E., Bur. PL Ind. Circ. no. 131. 



