82 LYCOPODIALES [CH. 



Specimens referred to this species were originally recorded 

 by Brodie from Rhaetic rocks in the Severn valley, the name 

 Naiadita being chosen as the result of Lindley's comparison of 

 the small and delicate leaves with those of recent species of the 

 •Monocotyledonous family Naiadaceae. The species may be 

 described as follows : 



Plant slender and moss-like in habit. The axis, which is 

 delicate and thread-like, bears numerous linear acuminate or 

 narrow ovate leaves reaching a length of approximately 5 mm. 

 Under a low magnifying power the thin lamina of the leaves 

 is seen to have a superficial layer of polygonal or rectangular 

 cells arranged in parallel series (fig. 136 h). There is no trace of 

 midrib or stomata. The sporangia are more or less spherical 

 and short-stalked, situated at the base of the foliage leaves and 

 containing numerous tetrads of spores. The spores have a 

 diameter of 0'08 mm. 



Buckman founded additional species on differences in the 

 shape of the leaves but, as Miss SoUas has pointed out, such 

 differences as he noticed may be detected on the same axis. 

 It was stated in an earlier chapter^ that Starkie Gardner, on 

 insufficient evidence, proposed to place Brodie's plant among 

 the Mosses. The discovery by Mr Wickes of new material at 

 Pylle hill near Bristol afforded an opportunity for a re-examina- 

 tion of the species : this was successfully undertaken by Miss 

 Sollas who was able to dissolve out spores from the matrix by 

 dilute hydrochloric acid, and to recognise the remains of internal 

 structure in the slender axes by exposing successive surfaces 

 with the aid of a hone. It was found that sporangia occurred 

 at the base of some of the leaves containing numerous tetrads 

 of spores, the individual spores having a diameter of O'OS mm., 

 apparently twice as large as those of any recent species of 

 Lycopodium. Fig. 136 shows a sporangium, a, at the base of 

 a leaf, b. Indications of tubular elements were recognised . in 

 the stem and it is noteworthy that although the outlines of 

 epidermal cells on the leaves are well preserved no stomata were 

 found. The leaves of the recent American species Lycopo- 

 dium alopecuroides Linn. var. aquaticum Spring^, which lives 

 1 Vol. I. p. 240. 2 Sollas (01) p. 311. 



