Report of State Board of Horticulture. 95 



thickly set with minute pimples or pustules. These are acer- 

 vuli and contain the spores of the fungus. These acervuli 

 begin to appear early in June. At first they appear as small 

 conical elevations of the epidermis which are scattered more 

 or less irregularly over the diseased bark. By the end of 

 June they have increased considerably in size and occasionally 

 one may be found which has burst open, thus exposing to 

 view the cream-colored mass of spores, which, however, soon 

 become dark colored. During July, August and September 

 the acervuli become more and more abundant and by the first 

 of November a very large proportion of .them has opened for 

 the purpose of discharging their spores. 



How carefully nature looks after her own and guards 

 against needless waste is well illustrated by this fungus. 

 Each acervulus contains thousands of spores, and were they 

 free to be distributed by the winds of summer, countless mil- 

 lions would perish before the arrival of climatic conditions 

 favorable for this germination. But the spores are not free. 

 They are firmly held in a gelatinous mixture which is com- 

 paratively dry and hard during the warm summer months, 

 but which, upon the advent of the fall rains, gradually softens 

 and dissolves, thus slowly liberating the spores just when 

 the conditions are most favorable for their germination and 

 growth. Once liberated the spores are doubtless distributed 

 by wind, rain and other agencies. 



A vast majority of the spores undoubtedly fall on uncon- 

 genial places and perish; but an occasional one may find 

 suitable lodgment in a suitable place on the bark of some 

 limb, and if temperature and moisture conditions are right it 

 germinates. The delicate germ-tube penetrates the epidermis 

 and after thus gaining access to the underlying tissues the 

 mycelium ramifies through them, spreading in all directions, 

 absorbing the nourishment upon which it grows, and killing 

 the surrounding cells. This distribution and germination of 

 spores, with the consequent formation of new cankers, may 

 continue from the time of the first fall rains until mid-winter 

 or later, but the most active period is during November and 

 December. During the winter, as previously stated, the 

 growth of the fungus and the consequent increase in size of 



