INTRODUCTIOI^ TO CRYPTOGAMIC BOTANY, 



893 



though sometimes more highly oxydised, and it is, in fact, the 

 elevation of portions of the crust into distinct pustular bodies, 

 which forms the grand distinction. The perithecia have often 

 a distinct ostiolum projecting beyond the outer surface, and 

 the resemblance to Hypoxylmi is sometimes so great as to 

 make an error almost excusable in a young botanist ; as, for 

 instance, in Trypethelium Sprengelii. The asci are well deve- 



Fig. 82. 



a. Pustules of Trypethelium Sprengelii, with sporidia. Communicated 

 from Ceylon by Mr. Thwaites. The endochromes of the sporidia are 

 irregularly imbricated. Above the left hand pustule is a separate 

 sporidium of T. cncenitim. Sent from S. Carolina by Eev. M. A. Curtis. 



b. Section of perithecium of Verrucaria variolosa, with sporidium. 

 From a Cayenne specimen sent by Dr. Montague. 



€. Thallus of Endocarpon lachneum, with vertical section and fruit. 

 Moug. and Nest., 442. 



d. Stegoholus Bei'heleiaims, Mont. A portion of the plant, with ascus 

 and two sporidia. Cuming Phil., No. 2185. 



All more or less mamified. 



loped, and the sporidia often very beautiful and complicated. 

 It appears to me that this mode of viewing the structure is 

 more simple, than considering the common mass in which the 

 perithecia are immersed an external perithecium. It is not 

 exactly homologous with the stroma of Hypoxylon, but it is 



