258 PROCEEDINGS OP THE AMERICAN ACADEMY. 



finally becoming much more deeply colored than the surrounding 

 threads. It is not, however, very easy to demonstrate, and many 

 sections must be examined before obtaining the fortunate ones vvliich 

 will show it. 



At first the fertile hypha presents no very characteristic form, but 

 as time goes on it becomes twisted sometimes almost spirally (Fig. 1). 

 Although usually simple in the beginning, later it may fork, or even 

 branch several times. This fertile hypha may be traced down in 

 among the mass of threads at the base of the primordium, and there 

 is nothing to indicate tliat it originates from any specialized organ, 

 but simply from the unditfereutiated mycelium. The subsequent 

 development of it which leads to the formation of the hymenium is 

 subject to some variation. In the smaller ajcidia the fertile hypha 

 simply begins to bud out at the tip into short projections which are 

 young basidia (Fig. 2), but in the larger lecidia it may branch so that 

 the hymenium may arise from several points (Fig. 3). In this 

 species the contents of the fertile hypha very soon {)ass into the 

 buds of the young hymenium, leaving it empty and quite indis- 

 tinguishable from the surrounding hyphaj. Following the develop- 

 ment of one of the smaller ^cidia, it is seen that the buds rapidly 

 increase in number and assume a more definite position. The larger 

 older ones are usually in the centre of the cluster, and the young 

 buds are formed around the periphery (Fig. 4). The young basidia 

 are cut oflT from the central mass as fast as they are formed, and 

 after enlarging somewhat show other cross septa, which are the first 

 indications of what may be called the spore mother cells. To make 

 room for the developing hymenium, the pseudo-parenchyma usually 

 splits at this juncture. A rift is formed in the centre of the primor- 

 dium, and, the cells around it collapsing, there is left a large cavity 

 into which the young basidia push up (Fig. 2). As the basidia in- 

 crease, they finally compress the pseudo-parenchyma, until in the 

 mature ascidium it is seen only as a narrow covering outside of the 

 peridium, made up of the collapsed and almost disorganized cells 

 which formerly filled the whole primordium. 



The development of the hymenium in the larger secidia is essen- 

 tially the same, except that in place of a single compacted mass of 

 basidia they arise over a somewhat larger area or from several distinct 

 points (Fig. 3). Soon, however, the basidia form a solid mass, and, 

 although there is a certain amount of intercalary formation, most of 

 the growth of new basidia takes place around the periphery of the 

 hymenium. 



