Fig. 135.—A Germinating spore of Physcia parietina with Protococcus viridis. B Synalissa symphorea with Glæocapsa. C Cladonia furcata with Protococcus.
The thallus of the Lichen appears mainly under three forms:—
1. The Crustaceous, which adheres firmly to the substratum (bark, stone) throughout its entire surface, without being raised into any free patches or lobes. It has, in many instances, no definite outline, and hyphal-branches from it often penetrate deeply into the substratum. It grows at the circumference and sometimes dies away in the centre (Figs. [138], [139], [140]).
2. The Foliaceous. This also lies flat upon the substratum, but is not firmly attached to and has a definite outline. It grows at the margin, and raises itself a little by free outgrowths and lobes (Fig. [141]). The rhizoid-strands spring out from its whitish under surface (Fig. [131], r).
Fig. 136.—Portion of a hymenium: d a thin stratum on which the asci (s) are situated.
Fig. 137.—Spores of, a Cladonia, Lecanora and Pertusaria; b Bæomyces; c Sphinctrina; d, e, f various species of Parmelia; g, h Verrucaria in its younger and older condition; i, k species of Leptogium.
3. The Fruticose, which is attached to its substratum at a small point from which it projects freely, either erect or pendulous. It is more or less tufted, in the form of a bush (Figs. [142], [143]). These three thallus-forms gradually pass over by many intermediate forms into one another.
