216 GENERAL CHARACTERS OF CRYPTOGAMS 



tissues, on account of which they are frequently used for scouring 

 purposes. Medicinally they have practically no use, although it is 

 said that poisonous properties exist in one or more of them. 



Lycopodiaceae. — The club mosses, like the horse-tails, are said to 

 contain some poisonous species, but their interest in drug commerce 

 resides wholly in the use of the spores of some species, under the name of 

 Lycopodium or vegetable sulphur. In the species yielding this product 

 there are two forms of leaves, those upon the fruiting portion differing 

 materially from those of the main stem (Fig. 598). In this group the 

 spores are all similar (Homosporous), while in some of the lower groups 

 they are of two forms (Heterosporous). As in the class last considered, 

 the gametophyte is microscopic, while the sporophyte is the con- 

 spicuous generation. Upon the upper surfaces, or in the axils, of the 

 leaves of the fruiting branch the spore-cases (Fig. 598, sp) are solitary. 

 In collecting Lycopodium, it is customary to pull off these tops and 

 allow them to dry thoroughly, whereupon the spores are easily shaken 

 out. 



The Filices. — The ferns contribute a number of important articles 

 to the materia medica, the principal of which is Aspidium, or Male 

 Fern. 



From a pharmacognostical viewpoint, the chief difference between the 

 ferns and the flowering plants is in the stem-structure. The main stem 

 is usually under ground, although often aerial and sometimes assuming 

 the dimensions of a shrub or tree. In the Hawaiian Islands these 

 trunks furnish timber for large and heavy planking. The peculiarity 

 of the fern-stem is its possession of a number of steles, each having 

 its own endodermis. As compared with the stem of an ordinary dicotyl- 

 edon, that of the fern presents the structural appearance of being a 

 fascicle of stems, bound together by an interstellar tissue. This indica- 

 tion is borne out by the peculiarities of the structures which fill the 

 office of the leaves of other plants, and which are known as Fronds. 

 While thus taking the place of ordinary leaves and appearing to be 

 such, these are seen, on closer examination, to be the homologues not 

 of leaves, but of stems, each of them originating from and representing 

 one of the steles of the compound stem. There is, moreover, no such 

 division of the stem into phytomers as we see in the flowering plants. 



It is not necessary to study the main stem in order to discover the 

 wide difference between the leaf and the fern frond, for if one but 

 watches the development and behavior of fronds, especially in certain 

 groups, as the Gleichenias, he will be struck by the fact that it is, in its 



