160 MORPHOLOGY. 



the development of the spores of the same plant. It is certain that 

 there is no difference perceptible between the development of the pul- 

 verulent and that of other Lichens ; and equally certain, that the so- 

 called paraphyses appear earlier than the sporangia, and that the latter 

 grow between the former, differing in their volume from the very begin- 

 ning, which proves that these paraphyses cannot be regarded as abortive 

 sporangia. Finally, it is evident that nothing appears in the whole 

 sporocarp but the paraphyses and the sporangia in different stages of 

 development. We cannot, for want of the necessary details, determine 

 what is meant by the so-called antheridia purporting to be discovered 

 by Link (indeed the statement rests only on an announcement in the 

 Prussian newspaper, Die preuss. Staatszeitung). The development 

 of the spores is very interesting in Lecidea sanguined. The young 

 sporangia have a very thick gelatinous wall, and the narrow cavity is 

 filled by a mucous mass (appearing in all Lichens), resembling intestinal 

 convolutions, in which from eight to twelve young spores are formed ; 

 of which only one, or occasionally two, are perfectly developed. In 

 time there appears upon the gelatinous wall of the sporangium a thicker, 

 more internal, lamella, formed probably by the pressure of the expanding 

 contents, which is gradually pressed outwards, and at length becomes 

 so blended with the outer bounding surface, that it alone encloses the 

 ripe spore. The ripening spore has likewise a gelatinous cellular mem- 

 brane, thickened in layers. The abortive, or more or less developed 

 spores often adhere to the perfectly formed spores, imparting to them 

 horns, points, or other strange excrescences. A few Lichen spores have 

 distinctly an outer coating of a hardened mucous substance. In Par- 

 melia parietina, for instance, this covering forms hollow hemispheres, 

 covering both ends of the spores, connected by a narrow strip of the 

 same substance (similar to the pollen-granules in Pinus). In Borrera 

 ciliaris the spores are of a dark, blackish-green colour, and it is dif- 

 ficult to determine whether this is produced by a similar coating, or is 

 due to the cellular contents. Owing to the almost general unanimity 

 that exists as to the use of the terminology, which is, to a great extent, 

 superfluous, I have given the most commonly used expressions in 

 parentheses. 



89. The anatomical structure of the Lichens is, generally 

 speaking, very simple. The most complicated, as, for instance, 

 Borrera ciliaris, consist of a three-fold layer. The principal mass 

 is formed of lichen tissue ; long, thin, dry, mostly forked, ramified, 

 and rather loosely interwoven cells (medullary layer), which curve 

 outward on the external surface, and, by degrees, pass into shorter 

 cells more closely packed together, and firmly connected by much 

 intercellular substance, and often into detached cells, the character 

 of which is with difficulty to be recognised as that of cells at all 

 (cortical layer). On the limit between the two lie larger or smaller 

 groups of roundish, cells, containing chlorophyll, and exhibiting, in 



(or, b, c), which correspond with the parts delineated in fig. 126. at a, I, c. We may 

 distinguish the layers of medullary and cortical layers of the plant in the sporocarp, 

 the layer of spore-cases at a still as the nucleus, and as a disc at b and c. Around the 

 nucleus at a there is a delicate layer of formative cells, which at b forms a base below 

 the tubular layer. At a the whole is enclosed in the layers of medulla and cortex ; at 

 b the latter layer only covers the disc ; at c this has also disappeared. 



