25 



(e) The Collemaceae are associated with Nostoc. 



(f) Ephebe and related genera with Stigonema. {Efhebella 

 Hegetschweileri with Scytonema.) 



(g) Hormogonium and Cystocolens are associated with an alga 

 belonging to the Confervaceae. 



(h) Graj)his, Opegrafha and related forms are associated with 

 Chroole-pus. 



4. The development of the spore never proceeds further than the 

 protothalloid stage, perhaps because of the absence of the requisite 

 algae. 



5. There is a great similarity between the lichens and the pyreno- 

 mycetous fungi. 



Schwendener issued a communication on the algal types of lichens 

 in the following year (81). It is accompanied by colored plates 

 illustrating most of the lichen-algae. Famintzin and Baranetzky 

 (23, 24) demonstrated experimentally that the gonidiaof heteromerous 

 lichens, such as Physcia, Evernia, Cladunia and Peltigera, as well 

 as some of the gelatinous lichens, as Collema, are capable of devel- 

 oping apart from the thallus, even producing zoospores like the uni- 

 cellular algae. In spite of this fact these investigators concluded that 

 the gonidia were not algae, and further expressed the opinion that 

 perhaps many of the unicellular algae were simply free lichen- 

 gonidia. 



Woronin (103) demonstrated that the gonidia of Parmclia ful- 

 verulenta never produce hyphal filaments, but always develop into 

 new gonidia ; or, what is the same thing, the free gonidium which 

 is neither more nor less than a species of Cystococcus develops into 

 new colonies of algae. He thus opposes the view held by Baranetzky 

 and Famintzin and favors the theory of Schwendener. Rees (74) 

 demonstrated that the hyphae developed from the spores of Collema 

 glaucescens will not mature unless associated with Nostoc lichenoides ; 

 in the absence of such an association the young hyphae soon perish. 

 A few years later Bornet (15, 16) isolated and determined specifically 

 the algae which enter into the composition of a large number of lichens. 

 He also described the method by which the hyphae envelop the 

 algae, as well as the mutual benefit derived from the intimate asso- 

 ciation of algae and fungi. Similar observations were made by 

 Treub (94). 



These and other experiments demonstrated beyond a doubt the 



