356 PROCEEDINGS OF THE ACADEMY OF [May, 



is correct, then the galls on the roots of Myrica are mycocecidia and 

 not mycodomatia, applying these terms as first suggested by Frank. 



The mycodomatia (PI. XVI) examined by the writer all grew upon 

 the short adventitious roots formed when the stems of the waxberry 

 bushes were covered by the blowing of the sand around them. On 

 some smaller secondary roots the galls simply dichotomize, but later, 

 by the increase in number of these forking fiber-Hke swelHngs, they 

 become aggregated together into nests or clumps about the size of a 

 walnut (PI. XVI). The dichotomous fibers that compose the myco- 

 domatia are of a rich umber-brown color. They grow in length by 

 small increments and repeatedly branch in a forking manner. On a 

 small stem examined, the fibers developed on the adventitious roots 

 surround the dry remains of the underground rhizomes of the marram 

 grass, Ammophila arenaria. The dead leaves and wiry stem of this 

 grass are mixed with the fiber-like galls by the repeated branching of 

 the galls among this material. The tips of the brown fibers that to- 

 gether form a fungovis household, or mycodomatium, are in the dried 

 specimens blunt and rounded. Their appearance seems to indicate 

 that, when fresh, they were of a lighter color and softer in consistency 

 than the older part of the swelhng. The fighter color of the tip prob- 

 ably indicates the growth of the year. A measurement of several such 

 apices shows that the growth is extremely slow, rarely exceeding a 

 millimeter or two in a single season. Some of the branches of the 

 mycodomatia measure twelve and fourteen millimeters in length. If 

 the yearly increment is one millimeter, such branches are twelve and 

 fourteen years old. If the annual growth is two millimeters, six or 

 seven years represent the age of some of the branches. A conserva- 

 tive estimate of the age of the mycodomatia that have reached 

 the size of walnuts is ten to fifteen years. If the growth in the length of 

 the branches of the mycodomatia is greater than this, then this esti- 

 mate is too high. One waxberry stem thirty-two millimeters in diam- 

 eter with several mycodomatia on its secondary roots shows twenty- 

 two annual rings of wood, and twenty years would be the outside limit 

 of the age of mycodomatia growing on such stems. When dried tlie 

 branches of the mycodomatia become extremely brittle, and the speci- 

 mens kept for the botanical museum suffered severely in being carried 

 from the seashore to the botanical laboratory. 



The microscopic structure of the galls is of interest because few of 

 the earlier observers seem to have determined satisfactorily the exact 

 character of the parasite. Thus Woronin" considered the parasite to 



" WoRONiN, loc. cit. 



