STUDIES IN THE GENUS GYMNOSPORANGIUM— I. 



NOTES ON THE DISTRIBUTION OF THE 



MYCELIUM, BUFFER CELLS, AND 



THE GERMINATION OF THE 



AECIDIOSPORE 



B. O. DODGE 



Columbia University 



The sporophytic mycelium of different species of Gymnosporangium 

 exerts an influence in connection with the growth of the tissues of the 

 cedar hosts which is manifested in a variety of ways. It is not clear 

 just why one species will cause the formation of a rather fleshy gall, 

 while another species will lead to the development of a witch 's-broom 

 or a hard, woody burl. A study of the interrelationships of host and 

 parasite, especially the more intimate association of the hyphae and 

 the host cells may help to solve some of these interesting questions. 



I wish to report briefly at this time the results of some studies 

 made to determine : (i) the distribution of the mycelium in an infected 

 leaf; (2) the possibility of its spread from leaf to stem; (3) the degree 

 to which it spreads up and down; (4) its distribution in wood, phloem 

 and cortex; (5) the distribution of haustoria. Four-nucleated 

 aecidiospore germ-tubes of Gymno sporangium transformans, and the 

 formation of buffer cells in the teleutospore sori of G. fraternum and 

 G. transformans will be noted. 



Farlow^ determined the general distribution of the mycelium in the 

 host for a number of American Gymnosporangia and described with 

 considerable clearness the primary effects of the parasites on the 

 tissues of the host plants. He found that the burls on Chamaecyparis 

 infected by G. hiseptatum are probably the result of a stimulation of 

 the cambium by the hyphae mainly distributed in the cambium region. 

 There appeared to be very little in the nature of a deleterious effect 

 of the parasite on this host. It was evident to him, however, that 

 the actual presence of mycelium in a given tissue is not necessary 

 to account for distortions or abnormalities. In G. Ellisii the fungus 

 interferes with the normal growth of the host, producing proliferations 

 and swellings of the stems and branches. This may be due to a dis- 

 turbance in the nutritive processes, the primary cause of which may 



' Farlow, W. G. The Gymnosporangia or Cedar Apples of the United States. 

 Am. Mem. Boston Soc. Nat. Hisc. 1-38. pi. i, 2. 1880. 



12s 



