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! and by Husemann and Hilger”. It isremarkable 
that the ash-constituent of Lichens is often very large, but on this point also information 
must be sought in special treatises®. 
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 Daetylococcus, 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) ; Seytonema 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‘ are Palmellaceae ; but Nostoe occurs with them in the Solorinae 

} 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, Pp. 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 heterolichenum, pp. 8-12. 
* Forssel has recently published an elaborate account of these occurrences. See Studier öfver 
Cephalodierna, in Abhandl. d. Schwed. Acad., Anhang. 8, Nr. 3, Stockh, 1883, and in Flora, 1884. 
