1919] Coit-llodyson : Abnormal Shedding of Washington Diavcl Orange 303 



configuration of the navel end, renders it reasonalily eertain that 

 infection occurs some time after the style has been shed. The spores 

 are probably blown and find lodgment in ragged open navels where 

 they arc lield in tlie crevices till enfolded and overgrown by the rapidly 

 developing ovary (pis. 34. 37). Ina.smuch as the configuration of the 

 navel as well as its size and degree of insertion are exceedingly variable, 

 it is evident that only in a comparatively' small and variable number 

 of cases are the spores or mycelium so situated as to permit germina- 

 tion or growth. Alirrnana citri is a weak para.site and cannot pene- 

 trate the unbrolicn skin of an orange. "While it is not capable of pro- 

 ducing any widespread breakdown in the tissues of immature oranges, 

 it is able, after introduction into the fruit, to bring about a certain 

 stimulus or irritation which, according to our theory, results in abscis- 

 sion of a eertain iiroportion of the young fruits. It is certain that as 

 the fruits grow and approach maturity tlie abnormal size, jireniature 

 ripening, and extra deep color are the direct results of this stimulation. 

 It is also considered highly probable that a certain proportion of the 

 .splitting or deliiscence of the carpels which is .so serious in interior 

 vaUeys is connected with the stimulation of these infections. 



Referring again to the wide distribution and general prevalence of 

 Allertmria spores in the air, it is evident that the spores may be trans- 

 ported in large numbers for great distances. The source of infection 

 is by no means limited to the vicinity of orchards. The fungus grows 

 readily as a sapliropliyte on dead leaves, weeds, twigs, and other plant 

 debris and it is entirely po.ssible for spores to be brought in from 

 forest areas in the mountains many miles away. Spores have been 

 taken in the desert far from cultivated crops. In the dry aii- of the 

 San Joaipiin Valley the black rot oranges which fall under the trees 

 are not immediately decomposed by I'cnicillia, Fusaria, and other fungi. 

 They tend to munmiify and after the Alternaria spreads through the 

 interior it comes to the surface, and the spores there formed give these 

 Diunnnies a black color, a.s shown in plate 38. These nuimmics. together 

 «ith the large number of aliscissed styles from the blossoms, undoubt- 

 edly furnish a gi-eally increased sui)ply of spores at the critical time 

 in the development of the fruit. 



A rot of apples occurring in Colorado'^ has been described as caused 

 by an undetermined species of Allcrnaria. Judging from the draw- 

 ings presented in plate 4 of Longyear's iiublication. the fungus is very 

 similar to if imt tlu' same as that with wliii'h we are dealing. ^Moreover, 



•■" Longyear, B. O., A Xew Apple Hot, Colorado Apr. Exp. St.n. Bull. 10.5, 

 1905. 



