DR. LAUDEU LINDSAY ON AETIIONIA MELASPEEMELLA. 283 



2. Fresenee of octahedral crystals of oxalate of lime in the 

 thallus, Nylander* thinks that this affords an additional test; and 

 it may constitute a corroborative feature in the crustaceous 

 lichens, in whose thallus this salt occurs in considerable quantity, 

 c. g. Urceolaria and Variolaria. But, so far as my experience ex- 

 tends, its presence is confined to the crustaceous thallus ; and the 



cmi 



Similar 



which are tzthalline and parasitic. 



• 3. Presence of starch-grains {Lichenine) in the thallus. 

 remarks apply here ; for though starch is to be found in con- 

 siderable quantity in the thallus of several of the higher Lichens 



< _ 



line forms. 



Cladonid) 



4. lUue reaction of tlie hymenial gelatine xmth iodine. What is 

 called, for convenience' sake, "liymenial gelatine," is really a 

 gummose amylaceous substance, known to chemists as lichenine. 

 It envelopes and lines, or occupies, the cavity of the thecce\ and it 

 IS chiefly in and on these, especially at their tips, gradually dimi- 

 nishing in intensity downwards, that the beautiful blue reaction 

 With solutions of iodine, characteristic of starch, is observable. 

 This lichenine, in the form of a colourless hyaline jelly, likewise 

 bathes the bases of the thecse and paraphyses, and is sometimes 

 intermixed w^ith the whole tissues of the hymenium. The blue 

 reaction is sometimes, therefore, observable principally at the tips 

 of the paraphyses, or at their bases, or. throughout their whole 

 extent; and it may be exhibited in the hymenial lichenine whca 

 there is no discoloration of the thecsD or paraphyses f. The 

 reaction of the constituents of the hymenium with iodine is, how- 

 ever, very variable in Lichens ; the colour developed may be any 

 shade [to .the faintest] of Prussian blue, violet, or wine-red ; and, 

 moreover, there may be no development or exhibition of colour 

 <it all', or it may be yellow ; or it may be that belonging to the 

 test or reagent itself. In certain groups or species of the Ver- 

 rucarice, for instance, the hymenium is ^waffected by iodine ; in 

 others, though exceptionally, a blue, yellow, violet, or wine-red 

 <?olour 18 developed, though generally very faintly. In K duliella, 

 Nyl., and V, endococcoidea, Nyl., two recent additions to the Scotch 

 Lichen-flora, the hymenial gelatine is wine-red with iodine ; while, 



* Lich. Scand. p. 14. 



t In a very few exceptional cases, e.g. in Oraj>his and Thelofrpma, some- 

 tunes, the lichenine enreloping the spores is the only scat of colorific reaction. 

 I have observed such a coloration [where the theccB were equally aficcfed] in 

 the spores of Parmelia megaleia, NjL, from the Sikkim-IIimalajas. 



