6 BOTANICAL GAZETTE [January 



of the individual filaments is more dense, and stains more deeply; 

 although this distinction becomes less marked in older individuals, 

 in which, however, the limits of the zone may be even more clearly 

 marked (fig. 14) through the often deep distal suffusion of the walls. 

 Above this line of demarcation in the upper zone, which simulates 

 an ascigerous hymenium, the walls of the upright tubes become 

 somewhat thicker, gelatinous, and tenaciously coherent; while 

 the protoplasm of each is segmented to form a series of short 

 cylindrical spores, which is constantly renewed and pushed upward 

 by the activities of the denser contents of the lower zone. The 

 spores separate from one another as they pass into a somewhat 

 paler region below the surface (fig. 12), becoming slightly rounded 

 at the extremities, with a few sometimes conspicuous granules. 



■ 



The discharge of these endogenous spores through the terminal 

 perforation of the tube has not actually been observed, but is 

 doubtless effected with some violence, the thickened walls around 

 the opening, and the mutual pressure of the gelatinous hymenial 

 elements, combined with the constant pressure from below, afford- 

 ing an effective mechanism for this purpose. The dimensions of 

 the sporogenous elements are very small, and owing to their gelati- 

 nous nature it is usually only with the greatest difficulty that the 

 limits of single tubes can be distinguished with exactness in sections, 

 or in crushed specimens; in fact no outlines are clearly defined in 

 this region, and even after staining, the minute spores are often 

 recognized with difficulty under high magnifications. The spores 

 do not seem to possess a wall, or if they have one it is so thin 

 as to be hardly demonstrable. Isolated spores are seldom 

 recognizable on the hymenial surface of healthy individuals, but 

 when the host is confined for a considerable period under some- 

 what unfavorable conditions, the normal discharge seems to be 

 interfered with, and it may become whitish with a coating of 

 extruded spores. 



At the periphery of the hymenium the sporogenous tubes 

 become sterile, thickened, and blackened, forming the inner portion 

 of the well defined, deep black-brown rim or exciple; while a narrow, 

 radiate, lichenoid margin spreads out externally from the base 

 (figs. 7, 8), in close contact with the surface of the host. 



