258 Rev. P. Keith on the External Structure 



that are not even aquatics, agreeing, however, in the common 

 character of having their herbage frondose, and their frond 

 for the most part without a root. 



Where a root exists, it is merely a fibrous or scutate base, 

 for the purpose, not of nourishment, but of attachment, as in 

 the Fuci. The frond is not uniform in its appearance through- 

 out the several divisions of the order. In the Tremellincce it 

 is gelatinous, as in Palmella nivalis — the substance that gives 

 colour to the polar snows * ; in the ConfervoidecE it is jointed 

 and filamentose; in the Ulvoidece it is membranous; in the 

 Fuci it is coriaceous, or leather-like ; and in the Lichenes, 

 which do not well associate with the rest of the Algcc it is 

 powdery, crustaceous, gelatinous, or even shrub-like. 



The fructification of the Algae is less perfectly known than 

 that of any of the preceding orders ; and yet it has received, 

 like them, considerable elucidation from the pen of Hedwig ; 

 but chiefly from that of more recent writers, among whom we 

 may specify the names ofVaucher, Agardh, Hooker, Greville, 

 Fries. " It consists merely of seeds or sporules in tubercles, 

 or in processes issuing from the frond, or immersed or more 

 or less scattered on the surface f." In the Lichens there 

 issues from the edge or general surface of the frond— thallus 

 — a number of small warts or tubercles, of the colour or con- 

 texture of the general herbage, and containing a multitude of 

 small granules, which Hedwig regarded as particles of pollen. 

 Later investigators regard them as being mere propagula, 

 From a different part of the frond there issues also a number 

 of cup-shaped or target-shaped substances — apothecia — con- 

 taining multitudes of small and minute granules, which Hed- 

 wig regarded as seeds. They are now reduced to the rank 

 of sporules. Several of the Fuci are edible and much re- 

 lished by many people whether raw or dressed : the Lichen 

 pidmonarius is employed in medicine, and the Lichen Perellus 

 in the art of dyeing. 



The Fungi, or Mushrooms. — The Fungi are a tribe of plants 

 whose herbage is a frond of a fleshy or pulpy texture, quick 

 in its growth and fugacious in its duration, and bearing 

 seeds or gems in an appropriate, exposed membrane, or con- 

 taining them interspersed throughout its mass. Plants of this 

 order are usually regarded as the lowest in the scale of vege- 

 table being, and as exhibiting a considerable resemblance to 

 the animal tribe of zoophytes. The habitats which they af- 

 fect differ with the spe'cies; some on the surface of the earth, 

 some buried under it; others on stumps and trunks of rotten 



* Hooker's British Flora, p. 454. f Ibid. 



