F UNO I. LICHENS. 



12,1 



from the third part of the female organ. The spermatia are produced in special 

 receptacles, the spermogonia ; these are cavities in the thallus, which are round or 

 flask-shaped or contorted, and densely lined or almost filled with sterigmata. The 

 spermatia are obtained by abscision from these sterigmata in large numbers, and 

 escape by a narrow opening in the spermogonium. 



The following details of the development of the apothecium are taken from the 

 gelatinous lichen Collema microphyllum 1 . The thallus forms a rim round the ripe 

 sporocarp, which therefore has an excipulum. The sporocarp consists of a firm 

 outside covering and a looser substance within. The apothecium in its earliest 

 stages exactly answers to the procarp of the Florideae, and is at first a stout lateral 

 branch on a hypha of the thallus. The basal portion is twisted like a corkscrew, 

 and above it is a long process which reaches the surface of the thallus and terminates 

 above it in a short point. The screw-twisted portion is the ascogone (archicarp), the 

 pluricellular filament which surmounts it is the trichogyne or trichophore-apparatus 

 (compare the Florideae). There are usually two and a half to three coils in the 

 ascogone, and a larger number of cells, on the average twelve. The number of cells 

 in the trichogyne varies with its length. It passes through the surface of the thallus 



FIG. 80. Vertical section of the gymnocarpous apothecium of Anaptychia ciltaris; h the hymenium, y the 

 Subhymenial layer (and excipulum) ; all beside belongs to the thallus of which m is the medullary layer, 

 rind,^ gonidia : at tt the thallus forms a cup-like border round the apothecium. Magn. about 50 times. 



he 



and terminates above it in a short point. The trichogynes appear only on the 

 side of the thallus which is exposed to the light. 



Admission of water causes the spermogonia to set the spermatia at liberty, and these 

 are spread over the surface of the thallus by the water-drops and so come in contact 

 with the sticky surface of the process of the trichogyne. Conjugation takes place 

 between them and the trichogyne, but it is not easily seen, owing to the extreme 

 minuteness of the objects. The ascogone is invested by a coil of the surrounding 

 hyphae, and its cells at the same time increase in size and multiply by intercalary 

 growth. The asci now grow out as lateral branches from the ascogone (archicarp), 

 while the rest of the parts constituting the apothecium are produced by a process of 

 vegetation which takes place on the hyphae adjacent to the ascogone. Thus the young 

 apothecium is composed of three elements : I. The ascogenous filaments ; 2. the 

 paraphyses, a system of hyphae running parallel to one another and at right 

 angles to the surface of the thallus and divided by transverse septa ; 3. the pseudo- 

 parenchymatous tissue, the 'excipulum proprium,' enclosing the other two. Fig. 81 

 gives a section through the apothecium of another Lichen, Anaptychia tiliaris ; the 

 explanation attached to the figure will be a sufficient description of the different parts. 



1 Stahl, Beitrage, Heft I. 



