The Anthracnose Disease of the Raspberry 167 



life history 

 The ascigeroiis stage 



During the season of 19 14 the fungus was kept under close observation 

 in order to determine when the ascocarps begin their development. 

 Repeated examinations of anthracnose lesions on young canes of the 

 purple-cane raspberry, at Brant, New York, showed that the ascocarps 

 begin to develop during the latter part of the summer. The sexual fruiting 

 bodies were found more commonly on this hybrid. The perfect stage 

 of the fungus has been collected by the writer also on the black raspberry 

 and the red raspberry, while Rees (1915) has reported it on the blackberry. 



About the middle of August, when the immature ascocarps are first 

 observed, they appear as minute spots, from deep brown to black, scattered 

 singly or in groups over the buff -colored and sunken part of the anthrac- 

 nose lesion. These spots are barely visible to the eye, and only visible 

 at all because of the contrast in color wath the surrounding tissue. At the 

 end of the winter the entire lesion assiimes a dark brown hue, and it is 

 with great difficulty that the fruiting bodies are then observ^ed, even with 

 a hand lens. 



In the early stages of its development the ascocarp is merely a raised 

 part of the stroma, the tissue of which is but slightly differentiated, and 

 the asci have not started to develop. A layer of brow^ cells covers 

 the fruiting body, forming a more or less circular structure which gives 

 the appearance of a shield, less perfect, however, than those found in the 

 family Microtheriaceae. The cells near the center of the shield are thinner- 

 walled, and with the further growth of the tissue within they soon split 

 apart in a stellate manner. By autumn the asci have appeared and are 

 found as globose bodies filled with a homogeneous mass of protoplasm. 

 In some instances the spores are formed by this time. The fungus may 

 pass the winter in this condition. 



In the autumn, or more often the following spring, the asci mature and 

 the homogeneous mass of protoplasm gives place to eight four-celled 

 ascospores. In the formation of these spores the middle septum is laid 

 down much earlier than the other two, and so it is not uncommon to find 

 two-celled spores. Later these two cells divide and the mature ascospore 

 becomes four-celled. The constrictions formed at the septa during this 

 second division are frequently not so great as at the first, or middle, septum. 

 Occasionally one of the cells fails to divide and an ascospore of three cells 

 is formed. 



During the formation of the spores the disintegration of the fungous tissue 

 about the asci takes place, and with the rupturing of the outer layer of the 

 ascocarp the asci are exposed. Frequently the asci lying in this exposed 



277 



