44 LYCOPODIALES [CH. 



leaf-bases, and presents the appearance of an irregular reticulum. 

 This arrangement of the mechanical tissue in the outer cortex 

 is comparable with that in stems of some species of Sigillaria. 



In certain species of Lycopodium the roots S which arise 

 endogenously from the axial vascular cylinder, instead of 

 passing through the cortex of the stem by the shortest route, 

 bend downwards and bore their way in a more or less vertical 

 direction before emerging at or near the base of the aerial 

 shoot. The transverse section of L. dichotomum represented in 

 fig. 125, A, shows several roots (R) in the cortex; they consist 

 of a xylem strand of circular or crescentric form accompanied by 

 phloem and enclosed by several layers of root-cortex. The roots 

 of Lycopodium do not always present so simple a structure as 

 those of L. dichotomum ; the xylem may have an irregularly 

 stellate form with as many as ten protoxylem groups. 



Reproductive Shoots^. In Lycopodium Selago the foliage 

 leaves serve also as sporophylls and, as Professor Bower^ has 

 pointed out, the branches exhibit to some extent a zonal 

 alternation of sterile and fertile leaves ; in other species, in 

 which foliage leaves and sporophylls are practically identical, 

 the sporangia occur sporadically on the ordinary leaves. In 

 species with well-defined terminal cones the lower sporophylls 

 may bear arrested sporangia and thus form transitional stages 

 between sterile and fertile leaves, a feature which occurs also 

 in the male and female flowers of many recent Araucarieae*. 

 The sporangia^ (fig. 126, D, F) are usually reniform and 

 compressed in a direction parallel to the surface of the cone- 

 scales ; they are developed from the upper surface and close to 

 the_J)ase of the fertile leaf to which they are attached by a 

 short and thick stalk (e.g. L. inundatum) or by a longer and 

 more slender pedicel (i. Phlegmaria, fig. 126, E). On maturity 

 the sporangia open as two valves in the plane of compression 



1 Strasburger (73) p. 109; Brongniart (37) PI. 8; (39) A. PI. 32: Brongniart 

 figures stems of L. Phlegmaria and other species showing roots in the cortex. 

 See also Goldenberg (55); Bruohmann (74); Saxelby (08). 



2 Since this was written a comparative account of the sporophylls of 

 Lycopodium has been published by Miss Sykes. [Sykes (08^).] 



3 Bower (94) p. 514; (08). « Seward and Ford (06). 

 ^ Goebel (05) p. 579. 



