i88 



DIVISION II. — COURSE OF DEVELOPMENT OF FUNGT. 



latter are placed perpendicularly to the surface of the hymenium, and terminate at 

 a uniform height on this surface, being crowded together in great numbers and 

 usually giving the hymenial layer its characteristic tint from the colouring of their 

 walls, or contents : not infrequently, especially in the hymenia of the Lichen-fungi, 

 they are united laterally and without gaps by the gelatinously thickened walls, so that 

 their lumina appear to be set in a homogeneous structureless jelly. The paraphyses 

 spring by their inner or lower extremities, that is, those turned away from the outer 

 surface as branches from a dense hyphal tissue beneath the hymenium, the subhymenial 

 layer or hypothcciiun, which is then continued further downwards into the more 

 or less largely developed recep/aculum or stipe of the apothecium, or at least 

 into an outer envelope, the excipulum, which belongs to it, though it is not greatly 

 developed. 



The paraphyses, together with the elements of the hypothecium which produce 

 and bear them and the receptaculum or excipulum, belong to the envelope-apparatus 

 of the apothecium. But the ascogenous hyphae take their course in the hypothecium, 



being interwoven with the ele- 

 ments of the envelope ; they 

 grow up in the commencing 

 apothecium from points of 

 origin, which will be described 

 more exactly in section LXIII, 

 in the direction of the hymenial 

 layer, and afterwards spread 

 themselves out near the under 

 surface of the disk with copious 

 branching which follows the 

 progressive growth of the whole 

 apothecium, and thrust the 

 extremities of their branches 

 of the last order successively 

 in between the paraphyses to 

 form the asci. In many of the species belonging to this division the ascogenous 

 hyphae can scarcely be distinguished from the elements of the envelope which 

 surround them by anything but the formation of asci which belongs to them only. 

 In others, especially in many but not all the Lichen-fungi, in which Schwendener 

 first discovered them, they are distinguished from the surrounding tissue by their greater 

 thickness, by the abundance of their protoplasm, and by their membrane turning 

 blue after treatment with potash. The development of the envelope-apparatus 

 is always in advance of the ascus-apparatus, though the latter may have begun to be 

 formed at the same time; the paraphyses are therefore always the parts which 

 are first present in the hymenium. The asci make their appearance after them 

 and grow vertically upwards between them in the direction of the surface, reaching 

 it usually or rising above it only as the spores become ripe (see section XXII). 

 Only a few asci appear at first, then their number increases through successive 

 branching of the ascogenous hyphae, often to such a degree that the paraphyses 

 are displaced and become indistinguishable. 



FIG. 87. Anaptychia ciliaris. Median section through an apothecium ; h hy- 

 menium, y subhymenial layer and excipulum. All beside belongs to the thallus 

 which forms a rim round the excipulum at / ; ?« medullary layer, r rind, ^-its Algae. 

 After Sachs. Magn. about 50 times. 



