316 COMPARATIVE MORPHOLOGY OF FUNGI 



Fragariae, where they may proceed to form conidia. In certain forms 

 they do not arise directly from the ground tissue of the fructification but 

 from large storage cells. Their fate varies in the different families. In 

 one they swell, as in many Sphaeriales, into a structureless gel, in another 

 they are persistent and partly intertwine over the tops of the asci to a 

 thin, brightly colored layer, the epithecium e; it is this cover layer which, 

 seen from above, gives the characteristic color to the apothecia. 



Besides the paraphyses in the hymenium of many forms there are 

 peculiar paraphysoid setae, which also belong to the haplont (not shown 

 in Fig. 208). While the true paraphyses are thin walled, hyaline and 

 multiseptate, the setae are thick walled, brown and always unicellular. 

 In the young stages they bend together (in the hemiangiocarpous forms, 

 after the rupture of the layer covering the young fructification) and form 

 a sort of sheath over the developing hymenium. Later they are pushed 

 aside and at most surround the disc. In the purely gymnocarpous 

 forms, whose hymenium is free and exogenous, they often remain scat- 

 tered over the hymenium during its development. In this case they 

 rise far below in the hypothecium and secrete a brown gluten at their tips. 

 This gluten flows over the surface of the hymenium, which in this case is 

 chiefly formed of the capitate ends of paraphyses, and there forms a struc- 

 ture which, at first glance, might be confused with the epithecium. In 

 this gel there often live a large number of bacteria which assist in the 

 rapid decay of the fructification. 



Under the hymenium is the hypothecium h, which forms the para- 

 physes directly and the asci indirectly. In some families the layer 

 which bears the hymenium, the hymenophore, is marked by a denser 

 structure or darker color; in systematic literature it is called the exciple. 

 In the ideal case, the hypothecium projects beyond the edge of the ascus 

 layer and forms the rim of the saucer or bowl pt; when this rim is 

 distinguished from the other tissue by a darker color, it is called a 

 parathecium. In certain forms the outer wall of the hypothecium is 

 pseudoparenchymatic and often darker in color (r in Fig. 208). 



The previously named layers and organs are all an inheritance of the 

 fungi; in the special case of the lichens mentioned here, they may be 

 surrounded by a thalline margin (exciple) which forms the amphithecium ; 

 this is usually similar in structure to that of the thallus of the lichen in 

 question and is generally composed of a cortex r, the algal layer a and the 

 medulla m, which is connected to the hypothecium either directly or by 

 a second algal layer. 



It is clear that in nature no apothecium has simultaneously all the 

 different layers here mentioned. In the lower forms, the apothecia are 

 of simpler structure and consist of a stromatic cushion, with an ascigerous 

 hymenium. In the higher forms they are much modified, so that the 

 fructifications in their histological differentiation, formation of latex 



