30 SOLORINA SACCATA. 



and '0035 inch in breadth. Our own measurements, taken with 

 great care from a large number of specimens, are much smaller, 

 viz. — '002 inch in the major axis, and •0006th inch across the 

 septum. The asci are placed in the midst of, and are protected 

 by, the paraphyses (literally, that which is produced beside, from 

 Trapd, beside ; (pvcng, a production), the coloured clavate apices of 

 which constitute the epithecium. As maturity approaches, the 

 asci ascend towards the epithecium, and there, bursting at their 

 apices, liberate the spores. All lichens which behave in this 

 manner are termed Gymnocai'pous (yvfivbg, naked, and Kap-n-og, 

 fruit) ; when the spores reach the surface through an opening or 

 chamber formed by a rupture of the extremities of the asci, the 

 lichen is denominated Aiigiocarpoiis (a term derived probably 

 from ayyaov, a vessel, and Kap-Kog^ fruit). After liberation, the 

 spore sends out numerous filaments or tubes, which, branching 

 and intertwining, form the hypothallus. Upon this body the 

 medullary layer and stratum-gonidiale are successively deposited, 

 after serving as the basis of which, it ultimately disappears. 



The apothecium is the latest development, and when this is 

 perfectly formed, the lichen has attained the highest state of its 

 organisation. In some species {e.g.^ Pet-tusaria commimis)^ this stage 

 may be never reached, and the thallus only obtains as a mere 

 powdery coating, the thickness of which varies according to the 

 circumstances under which it is produced. The lichen is then 

 termed ptilveriilent^ in which abnormal or abortive condition it 

 may continue for centuries, increasing by bisection, and com- 

 pletely veiling its base of support. In other species, the gonidia 

 penetrate the disc of the apothecium, which, in the genus Pertii- 

 saria, is thus rendered abortive by being converted into little 

 heaps or clusters of powdery bodies, called soredia. 



The apothecia of Solorina are never found growing parasiti- 

 cally upon the thalli of other lichens ; though parasitism some- 

 times occurs between other species. As an illustration, we might 

 name the genus Sphinctrina^ the stalked or sessile apothecia of 

 which are parasitic upon Pertusaria. This class of lichens should, 

 however, be carefully distinguished from entirely different species, 

 whose thalli grow beneath the epidermal layer of bark, or are 

 fleeting or evanescent ; such as some Cladoiiice^ Calicice^ and 

 Verrucari(Z. 



