380 



BOTANY. 



The stems are developed from a triangular apical cell, while the 

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

 of cells instead. The tibro-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. -4, vertical section of an archegonium and the rudimentary prothallium 



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 macrospore of Salvinia 

 natans at the commencement of germination ; p, the young prothallium. x 30. D, 

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

 membrane (m) adhering to it top view, x 200. E, a vertical longitudinal section of 

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

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

 same, surrounded hy 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 (OpJiioglossum pendu- 

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

 nearly three metres long (15 feet). 



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

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



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

 the Torrey Botanical Club, 1878; it is illustrated by figures. 



