380 



BOTANY 



and the ascogenous hyphae, although differentiated in the interior, do not succeed 

 in producing asci. 



In addition to the ascogenous fructifications, the Discomycetous Lichens 

 produce accessory fructifications in the form of pycnidia, which abstrict and 

 eject small conidia. Jig. 308 shows such a pycnidium of the common foliaceous 

 Lichen Anaptychia ciliaris. The pycnidia arise on the surface of the thallus 







Fig. 307. — Cladonki rangiferinu. A, Sterile ; 

 B, with ascus-fruit at the ends of the 

 branches. (Nat. size.) 



Fig. 30S. — Section through a pycnidium (sp) in the 

 thallus of Anaptychia ciliaris; c, cortical layer ; 

 ■hi, medullary layer ; g, gonidial layer. ( x 90.) 



(Fig. 308), or, as in Cetraria islandica, they may be produced on the margin in 

 small wart-like protuberances. In the Cladonias they occur on the same fructifica- 

 tions as the ascogenous hymenium or on others similar to them. The pycnospores 

 were formerly called spermatia, and erroneously regarded as male sexual cells ; the 

 pycnidia were then termed spermogonia. 



(b) The Pyrenolichenes or Lichenes angiocarpi have flask -shaped perithecia, 

 similar to those of the Pyrenomycetes, and also develop pycnidia. To this group 

 belong only a few, for the most part crustaceous Lichens (e.g. the Verrucarias, the 

 foliaceous genus Endocarpon, etc. ). 



2. Hymenoliehenes 



The Rymenoliehenes are represented only by the tropical Cora pavonia, of which 

 the genera Dictyonema and Laudatea are only specially differentiated forms. The 

 Fungus of this Lichen belongs to the family Thelephoreae (p. 370) ; its flat, lobed, 

 and often imbricated fructifications are also found entirely devoid of Algae. In 

 symbiosis with the unicellular Alga Chroococcus, it forms the fructifications of 

 Cora pavonia (Fig. 309), resembling those of the Thelephoras with a channelled, 

 basidial hymenium on the under side. Associated symbiotically, on the other 

 hand, with filaments of the blue-green Alga Scytonema, if the Fungus preponderates, 

 it produces the bracket-like Lichens of the Dictyonema form, found projecting 

 from the limbs of trees with a semicircular or nearly spherical thallus composed 

 of radiating hyphal threads, and having the hymenium on the under side. When 

 the shape of the thallus is determined by the Alga, a Lichen of the Laudatea form 



