ACROGENS. 



117 



like, by the intervention of a circle of bundles of elon- 

 gated cells, from which prolongations pass into the leaves, 

 so as to afford them a sort of midrib. 



FlG. 46. Ferns and their parts, a. Fronds and root-stalk, b. Frond, showing the 

 spore-cases, c. Exterior and interior of seed-vessel, d. Fronds, gradually unfolding, e. A 

 Theca, or spore-case, before opening, f. A Theca, or spore-case, discharging its spores. 

 g. Prothallus of its natural size. h. Lower surface of prothallus, much enlarged, showing 

 the organs whose reciprocal action determines the development of the fern. i. Various 

 forms of one of these organs when in movement. j\ Inclosed vesicle, in which the devel- 

 opment of the fern commences. 



The root-fibers are long tubular cells, quite transpa- 

 rent, within which the circulation of the bioplasm may 

 be seen. Dr. Hicks has observed portions of the inclosed 

 bioplasm detached, and having amceboid motions. 



