Til A I. LOG K.ns.] 



l.n iii:n \i.Ia 





hirta and plicata, Parmelia fraxineaand farinacea, and 

 obtained a substance called Usnine or I Bnic acid. This author I 

 and yellowish-green lichens are especially rich in uanL 

 graphics and Panneba sarmentosa. Usnine acts a cou 



metamorphoses and combinations in the alterations "i colour of many liclu an. I . 

 lichens however it i^ accompanied by yellow or green n sins, which in commou «itli it 

 partake of the property ol becoming red by ammonia and exp 

 colouring how< ver is di stroyed bj sulphuretted hydrogi u. I snin 

 as well a.i in the fruit-discs. The shields "l 1 1 1 ■ - Cladoniaa contain near the fruil I 

 resides quill-shaped cyUndrical cells, which are coloured pale red at the l 

 darker towards the apex by a colouring Bubstance, which dissolves in ammo 

 potash with a wine-red, in sulphuric acid with a carmine-red colour; the sulphatic solu- 

 tion is precipitated by water ; the alkaline solution is not decolorized by Bulpl 

 hydrogen. The marly scarlet-red fruit-discs <>f the Cladonue become brown 

 blackish-brown with age. In fact, the fruit-discs of the lichens containing usnini 

 precisely similar in colour t<> the thallus, or brown, reddish-brown and earn 

 The Bulphur-yellow lichens contain most usnic acid, and indeed in a free state ; • ■ 

 colon - are probably prodw ed bj the action of the alkalies and earths "t tin vegi table 

 salts in the lichens, the ammonia of the rain-water assisting the chemical action "t the 

 ic acid, which is othen luble in water. In this manni ,ud 



ty originate. The ail v< ted myce rangiferina probably i 



the usnic acid in the Btate oi an earthy ^alt. Lecidea geographic 

 Bulphur-yellow, Bometimes yellowish-green. If some pure yellow specii 



pended in a glass ovi r a solution of carbonate of ammonia, they becom ivered \siili 



carmine-red globules, after frequent washing entirely I"-'- the usnic acid, and finally 

 !>• come grayish-white like dead lichens. The Parmehaa and I -■■ i c mtinue • 

 brilliant gre id colour in Bhady and moist places, but when < xposed t" thi 

 sun they become brownish-black; if treated as above with ammonia and drii 

 likewise present mmilar colours. Tlu- fruit discs of the Cladoniss also turn brown m 

 similar treatment The cause of all these changes is the usnic acid, which it- II 

 yellow colour, but becomes oxidized in combination with bases by < xposure to the air, 

 forming various coloured compounds. C 



I \\\lll* 



In this, as in the Fungal alliance, 1 have forborne formall) to break u 

 several Natural orders, and have pri ferred to leave thi 

 myself in this branch of Botany ; bul it is not to be d il 



Mr. Berkeley, i- not avi rse to this reduction. Ti I 

 the tin it ol a Lichen, rhe following 



Collema, Ach. 



1 aim, ^V 



.Vry. tl\ 



■ 



Fr. .mi, 



Mysopunua, .'.' 



Dm: 



It is better for the present, in a man 

 a hint, rather than to propose a distinct natural order. U 

 icing them apart under some kind of denomination. 



lig. XXXIII*.— Parmelii 



