LYCOPODIACE^ 59 



periphery lie the bast-like cells known as ' protophloem-elements.' 

 Within the bundle-sheath the phloem is surrounded by several layers of 

 larger cells, corresponding to the phloem-sheath of ferns. Though the 

 sclerotised tissue is much less developed than in ferns, the axial ' vascular ' 

 bundle is, in the stouter species of Lycopodium, surrounded by a ring 

 of fibres composed of several layers. The axial bundle is cauline, and 

 may be followed out, in a rudimentary condition, to very near the apex. 

 In Phylloglossum the short stem is traversed by a single narrow bundle, 

 which is very weak, and has no scalariform, only a few spiral and 

 annular tracheides. 



The roots of Lycopodium originate on the outside of the axial 

 cylinder ; their internal structure is similar to that of the stem. In the 

 erect species they have their origin at a considerable height in the stem, 

 whence they strike downwards through its fundamental tissue, in which 

 they sometimes even branch dichotomously, and emerge in the form of 

 a tuft at the base of the greatly thickened stem. In the creeping and 

 climbing species they emerge separately, and dichotomise in the soil 

 in intercrossing planes. The epiderm of the root is often strongly 

 cuticularised. In Phylloglossum the underground portion of the stem 

 consists of two ovoid tubers of different age (see fig. 38), which are 

 destitute of the least trace of ' vascular ' bundles. From above these 

 tubers spring a few adventitious roots, which are of endogenous origin, 

 do not branch, and each of which has a single concentric axial bundle. 



The leaves are very small in most species of Lycopodium, and 

 invariably narrow, simple, and sessile ; sometimes with a long apiculus. 

 They are sometimes adpressed to the stem with the exception of the free 

 apex ; more often they are entirely free. In some species the form 

 and size of the leaves vary greatly even on the same individual plant, 

 and these heterophyllous species often display more or less of a bilateral 

 structure. The phyllotaxis is sometimes verticillate, sometimes spiral, 

 or both arrangements occur together in the same species. In the 

 verticillate species the leaves are either decussate, or in whorls of three, 

 four, or more ; on creeping stems they are usually placed on a transverse 

 zone oblique to the axis ; and the number of leaves in a whorl varies 

 even on the same branch. The small and extremely variable divergences 

 of the leaves in the species with spiral phyllotaxis are very remarkable. 

 Each leaf is always penetrated by a single central ' vascular ' bundle 

 without any lateral branches ; it is of very simple structure, and is in 

 connection with the axial cylinder of the stem. In L. albidum (Bak.) 

 the leaves are membranous, and quite destitute of chlorophyll. The 

 epiderm is provided with stomates, either on the under surface only or on 

 both surfaces, and frequently collected into groups. The fundamental 



