174 LICHENS A.ND MOSSES. 



nent of Europe. Others, however, are very poisonous ; and it is believed that species 

 which are sometimes wholesome become poisonous when grown under other con- 

 ditions, or eaten by persons of peculiar sensibilities. Upon the whole, it is a class 

 of plants which should be sedulously avoided, although a very considerable number are 

 known to be edible in various parts of the world. The dry rot is due to the Polyporus 

 destructor, and other species ; the blight of corn to the Puccinia graminis ; the rust to 

 the Uredos and Puccinise ; and the mildew to the Mucedos (Fig. 301). They also attack 

 cheese, bread, preserves, fruit, and almost every article of food, and are then known as 

 mould ; and it is a curious fact that the presence of any perfume prevents their forma- 

 tion. A few of them are phosphorescent. The number of genera is so vast that it is 

 useless to attempt any very limited selection, 



These are directly opposed to Fungi, inasmuch as they are perennial, and consist of 

 a lobe and leaf-like thallus. They constitute the gray, yellow, and brown stains which 

 give an air of antiquity to the walls of our churches ; or they are found on broad patches 

 of a leprous appearance on the trunks and branches of trees. They are useful to 

 man in two modes first, by affording dyes as described on page 54, and, secondly, as 

 food. The latter quality is found in the Cetraria Islandica or Iceland Moss, Cenomyce 

 rangiferina or Keindeer Moss, Sticta pulmonacea, Alectoria usneoides, and various 

 species of Gyrophora, which furnishes food to the Canadian hunters. Many others 

 possess medicinal properties of value. It is an extensive family of plants, but hitherto 

 it has not been studied with the care which has been bestowed upon other, but not less 

 valuable and interesting, vegetable productions. 



MOSSES. 



This great class is subdivided into several portions, and exhibits a degree of organ- 

 ization considerably beyond those to which we have hitherto referred. Amongst the 

 subdivision we may instance the Scale Mosses (Jungermanniae), Split Mosses (An- 

 draeacea), Urn Mosses (Bryaceae), Club Mosses (Lycopodiacea), Crystal Worts (Ric- 

 ciaceae), Liver Worts (Marchantiaceae), and Horse-tails (Equisetacea). In some 

 instances, as in the Sphagnum and Polytrichum, the male organs may be seen in con- 

 stant motion in the early spring months, and appear like two thread-like bodies, with 

 one extremity thin and attached, and the other enlarged and free, inclosed within a 

 distinct cell-wall. The same kind of motion is also found in other members of the class, 

 and is due in some degree to hygrometric influence, as has before been described in 

 reference to the Urn Mosses. 



The Crystalworts are amongst the most diminutive members of the class, and swim 

 or float upon small collections of shallow water, or attach themselves to the mud. 

 They are but few in number. The Liverworts are found very abundantly in damp 

 unfrequented places, on the uncovered ground, inclosed by the walls of ruined castles. 

 They consist of a broad frond, which lies upon the soil, and emits roots from its under 

 surface, possessing antheridia and pellate receptacles. They differ from Crystalworts 

 in having elaters and involucrate spore-cases. 



The Scale Mosses (Jungermanwia, Figs. 294 and 29o), possess a far higher degree of 

 organization, having well and symmetrically expanded leaves, and, in many, a long 

 Btalk supporting the simple fruit. They abound in tropical regions. 



The Horse-tails (Equisetum) possess a fistular articulated stem, surrounded by 



