LYCOPODIACE.E. 



419 



surrounds the axial cylinder; in L. Chanmcyparissus this thickening of the walls is 

 remarkably great (Fig, 310 ^)\ 



. The epidermis of the stem consists, in Selaginella, of long prosenchymatous cells, and 

 has no stomata ; these occur only in a few rows on the under side of the leaves ri<^ht 

 and left of the mid-rib (Fig. 46, p. 47). The epidermis of the leaf consists of cells 



Fig. -ixz-Sela^uella inaqualifolia ; longrituclinal section through the right side of the axis of a spike S, the base 

 of the leaf*, the ligule «, and the sporangium^/; ^ point where the cauline and foliar fibro-vascular bundles unite; 

 /air-conducting intercellular spaces ; -I' series of cells traversing the spaces. 



containing chlorophyll, the lateral walls of which are beautifully serpentine. In L. Selago, 

 on the other hand, the large and comparatively few stomata are distributed over the 



^ [Hegelmaier, in an exhaustive treatise on the morphology of the genus Lycopodium (Bot. 

 Zeitg. 1872, p. 773 et seq.), describes the stem as consisting of a fibro-vascular cylinder surrounded 

 by a thick cortex, the first being fonned of a number of bundles penetrating a thin-walled and 

 narrow-celled tissue. The central cylinder is composed of two parts, distinguishable from an early 

 period and even when the tissue is mature, viz. a comparatively small external and a much more 

 strongly developed axial portion, the latter consisting of the true fibro-vascular bundles with mter- 

 fascicular tissue. The first of these two parts, which must not be confounded with the inner layers 

 of the cortex, surrounds the central part of the cylinder as an enveloping sheath, and Hegelmaier 

 proposes for it the term 'Phloem-sheath,' retaining, with previous writers, that of ' phloem ' for the 

 interfascicular tissue. This phloem-sheath (Fig. 310 B,p) is separated from the phloem by a cylin- 

 drical layer which unites together the outer convex surfaces of the fibro-vascular bundles, and is 

 distinguished from it by its cells being shorter, with thinner walls and larger cell-cavities.— Ed.] 



£62 



