FUNGI. 



273 



view that the gonidia are true Algae, since the proofs of this are over- 

 whelming. 



Reviewing the views of older lichenologists, which may be found represented in 

 detail in the writings cited below of Baranetzky and Schwendener ; it may be mentioned, 

 first of all, that De Bary (Handbuch der phys. Bot. vol. II. p. 291) had already arrived 

 at the following alternative with respect to gelatinous Lichens, as Ephebe and similar 

 forms: — 'Either these Lichens are the perfectly developed fructifying states of plants the 

 incompletely developed forms of which have hitherto been placed among Algae under 

 the names Nostocaceae and Chroococcaceae, or these last are typical Algae which assume 

 the forms of Collema, Ephebe, &c. Certain parasitic Ascomycetes penetrate them, 

 extend their mycelium into the growing thallus, and often form an intimate attachment 

 with those of its cells which contain phycochrome (as Plectospora, Omphalaria). 

 In the latter case these plants may be called Pseudo- lichens.' From the last 

 sentence of this quotation it follows that E^ Bary would not apply the latter alter- 

 native at all events to the heteromerous Lichens. Soon afterwards Famintzin and 

 Baranetzky, and then the latter alone, published researches on the further changes 

 which the gonidia of Lichens undergo when they are set free by the decomposition of 

 the hyphal tissue in water\ Baranetzky comes to the conclusion that: — 'The gonidia 

 of the heteromerous chlorophyll-containing Lichens (as Physcia, Evernia, Cladonia, &c.), 

 as well as of the heteromerous forms which contain phycochrome {e.g. Peltigera), and 

 of the gelatinous Lichens (such as Collema), are capable of carrying on an entirely inde- 

 pendent life outside the Lichen-thallus. When set free the Lichen-gonidia appear to 

 expand their cycle of life ; and thus the independently vegetating gonidia of Physcia, 

 Evernia, and Cladonia produce zoospores.' He also found that all the ball-like masses 

 of Peltigera-gonidia were afterwards transformed so as to become extremely like the 

 interstitial cells of a Xostoc ; and he did not doubt that this was their permanent 

 condition. ' Some, perhaps many, of the forms hitherto described as xA.lgae must be 

 considered as independently vegetating Lichen-gonidia, such as, for the present, the 

 forms Cystococcus, Polycoccus, and Nostoc' The researches of Schwendener, carried 

 on in part earlier in part simultaneovisly and later, and conducted in the most careful 

 manner, led to the opposite conclusion, that the gonidia are in fact Algae which are 

 more or less disturbed in their manner of life by the Fungus which becomes parasitic 

 upon them. He first stated in the frankest and clearest manner that this was 

 his opinion with respect to all Lichens in his treatise ' Ueber die Algentypen der 

 Flechtengonidien' (Basel 1869). In this memorable \vork, which settled for the future 

 the systematic position of the Lichens atnong the Ascomycetes, he gives a review of 

 those genera of Algae which were up to that time known as hosts of Lichen-fungi, in 

 other words, as playing the part of gonidia : — 



I. Algce ~.vith Blue-green Contents {NostochinecB). 



Name of Group of Al^^.x. Lichen on which they occur as Gonidia. 



(i) Sirosiphoneae . . Ephebe, Spilonema, Polychidium. 



(2) Rivularieae . . Thamnidium, Lichina, Racoblenna. 



(3) Scytonemeae . . Heppia, Porocyphus. 



(4) Nostocacese . . Collema, Lempholemma, Leptogium, Pannaria, Peltigera. 



(5) Chroococcaces . Omphalaria, Euchylium, Phylliscum. 



1 Memoires de 1" Acad. Imp. des Sci. de St. Petersbourg, 7th series, vol. XL no. 9, Jind Melanges 

 biologiques tires du Bulletin de I'Acad. Imp. de St. Petersbourg, vol. VI. 1867.— [Ann. des Sci. Nat. 

 5th series, 1867, vol. VIII. pp. 137-144.]— Also Itzigsohn, Bot. Zeitg. 1868, p. 185. 



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