284< 



INTRODUCTION TO CRYPTOGAMIC BOTANY. 



various colours, as green, purple, vermilion, &c., a circumstance 

 which never takes place amongst the Splueriacei. In the 

 linear^species the form of the aperture depends upon the fomi 

 of the perithecium, or excipulum, the margins of which are 

 rounded. In other cases, however, the disc is exposed by the 

 mere^ fissure of the walls, as in Phacidium, and this fissure 

 may either be simple or compound, radiating from a central 

 point and forming triangular lobes. 



Fig. 66. 



a. Eysferium Fraxini, P. Perithecium entire and divided vertically, 

 with ascus and sporidia, 



b. Phacidiv.m Delta, Kze. Perithecium and asci with sporidia. From 

 specimens gathered in Madeira by the Rev. R. T. Lowe. 



c. Ascomyces bullatus, Berk. From the ninth volume of the Journal 

 of the Hort. Society of London.* 



d. Vihrissea truncorwn, Fr., nat. size, and sporidia. From a sisecimeu 

 sent by Eev. T. Salwey, from Llyn Howel. 



293. The species are numerous, but by no means so multi- 

 tudinous as the SpJueriacei. The walls of the perithecium 

 are either carbonaceous or cartilaginous, and very rarely soft, 

 in which case they must be separated with caution from the 

 Pezizce. When the hymenium is well exposed, as in Cenan- 



* A species of this genus distorts the leaves of peaches in a most ex- 

 traordinary way. The increase in thickness is caused by the inter- 

 position of eight or more strata of merenchymatous cells between the 

 cuticidar stratum, and the oblong close-packed cells, which in healthy 

 peach-leaves follow it. At the same time the intercellular spaces of the 

 lower part are narrowed as the leaf contracts. 



