CHAPTER VII. PHENOMENA OF VEGETATION. LICHENS. 409 



lechia tartarea, Mass., in Urceolaria scruposa which has an enormous number of crystals 

 occasionally of large size in the interstices of the medulla, and in Thalloidima candidum 

 where granules are found both on and in the upper side of the rind ; the thallus of the 

 Pertusarieae, especially Pertusaria fallax, contains large, irregular, interstitial crystalline 

 masses ; granular incrustations are found in the medulla of Chlorangium Jussuffii, and 

 smaller isolated crystals are scattered about in the interior of the thallus of Megalospora 

 sanguinea and M. affinis, Mass., Ochrolechia pallescens, Mass, and other species. 



Yet it would be incorrect to say that calcium oxalate occurs in all Lichens, or always 

 in the octahedral form. It does not even occur in all crustaceous forms ; I have as yet 

 looked in vain for it in Lecanora pallida and in Lecidella enteroleuca, Kbr. Neither 

 Schwendener nor myself have found it in any foliaceous species except Placodium and 

 Endocarpon monstrosum mentioned by Schwendener, and we both noted its absence 

 in most fruticose forms. In the young branches only of Roccella fuciformis I have seen 

 tolerably large crystals which were not however chemically examined, and groups of 

 small rods and granules composed of the salt in question in the rind and medulla of 

 Thamnolia vermicularis. 



This is not the place for a full enumeration and description of the substances organic 

 and inorganic which analysis has detected in Lichens ; the facts have been collected 

 and the literature noticed by Rochleder 1 and by Husemann and Hilger 2 . It is remarkable 

 that the ash-constituent of Lichens is often very large, but on this point also information 

 must be sought in special treatises 3 . 



The Algae of the heteromerous thallus in the majority of species are chlorophyll- 

 green ' Palmellaceae ' ; Cystococcus is the Alga in most of the Parmelieae ; Pleuro- 

 coccus has been determined by Stahl in Endocarpon pusillum and Thelidium minutulum, 

 and;Stichococcus in Polyblastia rugulosa ; Bornet has determined the Alga in Solorina 

 saccata and possibly also in S. crocea, Nephroma arcticum and Psoroma sphinctrinum, 

 Nyl. to be Dactylococcus, Nag., and in Sticta glomulifera, Ach. he conjectures it to 

 be an Ulothrix. It will be seen that a considerable variety of species are known to 

 occur in Lichens, and it is desirable that the Algae should be isolated and more exactly 

 determined in other forms which have only been hastily examined. Roccella has a 

 species of Chroolepus for its Alga. The Nostocaceae and Chroococcaceae which owe 

 their blue-green colour to the presence of phycochrome are peculiar to many hetero- 

 merous Lichens ; species of Nostoc according to Bornet's more or less certain 

 determinations occur in Nephromium, Nyl., Peltigera, Stictina, Nyl., and in the species 

 of Sticta which have blue-green Algae, the remaining species being formed with Algae 

 from the group of the Palmellaceae (Fig. 173) ; Scytonema is the Alga of Coccocarpia 

 molybdaea, Pers., and blue-green Algae of undetermined species are the Algae 

 of the Lichen-genera Psoroma and Verrucaria. 



The thallus of some heteromerous Lichens is peculiar in including a second Alga 

 in addition to the species which is its principal and constant constituent. The chief Algae 

 in Solorina saccata and S. crocea, some species of Stereocaulon, Sticta glomulifera 

 and some others 4 are Palmellaceae ; but Nostoc occurs with them in the Solorinae 



1 See Gmelin's Handb. d. Chemie, VIII. 



2 Die Pflanzenstoffe. 



3 Thomson in Ann. d. Chem. u. Pharm. 53, p. 254. 



Knop in Erdm. Journ. f. pract. Chem. 38, p. 46 ; 40, p. 386 ; and in Ann. d. Chem. u. 



49, p. 108. 



Giimbel, Ueber Lecanora ventosa (Denkschr. d. Wiener Acad. Math. Naturw. Cl., XI). 

 Lindsay, Popular Hist, of Brit. Lich. p. 51. 

 Uloth in Flora 1861, p. 568. 

 Th. Fries, Genera heterolichennm, pp. 8-12. 



4 Forssel has recently published an elaborate account of these occurrences. vSee Studier Sfver 

 Cephalodierna, in Abhandl. d. Schwed. Acad., Anhang. 8, Nr. 3, Stockh. 1883, and in Flora, 1884. 



