380 



BOTANY. 



The stems are developed from u triangular apical cell, wliile the 

 roots, like those of Marattiirem, possess no apical cell, but a group 

 of cells instead. The Gbro-vascular bundles are arranged in a cylinder 

 (a circle in cross-section), and they form a network by their anastomos- 

 ing with each other. According to De Bary, they belong to the "col- 

 lateral " series. 



These plants are usually of small size, rarely exceeding 30 centime- 



Fig. 271. — A, vertical section of an archpgonlum and tbe rudimentary protlialliuni 

 of FUvlaria fflobulifera : w, w, part of the ruptured wall of the macrospore ; p, p, 

 the rudimentary prdthalliura. merging above into the arcliegonium ; y, the germ-cell 

 ready for fertilization ; ac, the cavity of the macrospore. X 500. B. a microspore 

 of the same burst open and allowing the escape of sperm-cells. «, from which sper- 

 matozoids are escaping. X 600. C, longitudinal section of a macrcpore ol Salvinia 

 naiam at the commencement of germination ; », the young prothallium. x 30. D, 

 a very young prothallium of the same, detached, with a fragment of the inner spore- 

 membrane (rrC) adhering to it— top view. X 8P0. E, a vertical longiiudiral section of 

 D, X 200. F a similar section of a more advanced prothallium of the same ; g, the 

 young germ-cell. X 200. (?, vertical section of an unfertilized archegonium of the 

 same, surrounded by cells of the prothallium ; g, germ-cell ; ar, canal of the arche- 

 gonium. X 300.— After Hofmeister. 



tres (1 foot) in height ; in one Ceylonese species (OpliiogTo&SMm pendu- 

 lum) the slender pendent leaves are sometimes, according to Hooker, 

 nearly three metres long (15 feet). 



There are three genera, viz., Ophioglossum, BotrycMum, and Helmin- 

 Ihostachys ; the latter is confined to the southern hemisphere, the others 



U. E. Davenport's paper, Vernation in Botrychia, in the Bulletin of 

 th» Toi-rey Bolcfnicfil Club, 1878 ; it is ijlust^ated by figures, 



