167 



is alike throughout the year. The exterior leaves decay slowly and 

 in order of priority, the decay commencing in each leaf about an inch 

 above the crown of the rhizoma and extending upwards and down- 

 wards ; the decayed portion soon loses its rigidity, the upper part 

 bending over and becoming prostrate. The leaf retains its at- 

 tachment long after its vitality has ceased ; and numerous leaves so 

 attached fall over the tuber and its radicles when the plant is taken 

 from the water, and, mingling with the latter, are preserved as such 

 in most of our herbaria. Leaves in a state of decay are shown in the 

 figure at the head of this article. 



The fnictification of the Quillwort is very curious. It consists of 

 capsules or thecal, about the size of swan-shot, placed singly at the 

 base of each leaf, in the very substance of which they are imbedded ; 

 only a very small portion of the capsule being visible through a circu- 

 lar aperture in the anterior face of the leaf. In this structure alone 

 does it differ fi-om Lycopodium, in which genus the theca is quite 

 distinct, although perfectly sessile in the axil of the leaf, and remov- 

 able without injury to the leaf itself. The sub- 

 stance of the theca is hard though membranous ; 

 it is attached at a single point {b) on its posterior 

 surface, to something which appears analogous 

 to a midrib of the leaf The figvu-e in the mar- 

 gin represents a theca removed from its cavity in 

 the leaf: from its point of attachment (b) arise 

 what appear to be two free placentae {a a), for the 

 attachment of the seeds, yet I cannot positively assert that such is 

 their office, for I have never opened a theca without observing that 

 the seeds escaped, as if entirely without attachment. Wahlenberg 

 speaks of these bodies as being many;* from this statement, and that 

 author's surpassing accuracy, I am inclined to suppose the few theca) 

 which I have had the opportunity of examining in a recent state to 

 be exceptions to the general mle, especially as in the generic charac- 

 ter of Isoetes in 'English Flora' (iv. 343), Sir J. E. Smith describes 

 the capsule of the fertile flowers as having " several transverse bris- 

 tle-shaped bars." The seeds themselves are rugose and perfectly 

 white ; they have raised ridges on the surface, indicating a quadruple 

 division ; indeed, when thus divided, the inferior half of each seed is 

 nearly hemispherical, and the superior half may be again divided into 



* Ex illo receplaculo fructus longitudinali oiiuutur plura receptacula scminum scu 

 narlialia fiiliformia, &;c. Fl. Lap. 295. 



