SPECIAL MORPHOLOGY: FERNS. 



195 



tute a cellular wall, and the internal ones parent cells (sporangia) for 

 the spores, being absorbed soon after the latter are perfectly de- 

 veloped and have been invested with a special membrane covered 

 with warts or folds. From the parietal cells a series of cells is 

 formed, running either vertically or obliquely from the pedicle 

 almost entirely round the capsule, or forming a horizontal zone at a 

 greater or lesser distance from the top of the capsule, and in such a 

 manner that its inner, and upper and lower contiguous walls become 

 very much thickened, while the other walls remain thin. These 

 cells constitute what is termed the ring (annulus) ; by its unequal 

 contraction in drying, the capsule is opened for the escape of the 

 spores. In other Ferns the small quantity of parenchyma developed 

 around the nerves forms in its interior groups of parent cells and 

 spores, so that the lobules of the leaf swell spherically into capsules, 

 and, occasionally bursting open by means of an imperfectly com- 

 pleted ring, shake out the spores (as, for instance, in Ophioglossea, 

 Osmundacecs). 



B. It is only in the proembryo of Ferns that we find organs simi- 

 lar to the antheridia of Mosses and Liverworts ; here they occur 

 either upon the margin or upon its upper surface, and are most 

 spherical and unpedicled. 



By way of illustration of the above, I will give circumstantially the 

 delineation of a part of the spore-leaf of Pteris chinensis (fig. 145. A, B), 



145 



and of Adiantum pubescens (fig. 145. (7), as well as an analysis of the cap- 

 sule of Scolopendrium qfficinarum (fig. 146.). 



145 Pteris chinensis. A, Part of the spore-leaf: a, b designates the direction of the 

 section. B .- a, b is the leaf; c c its thickened margins ; d d, folds of the margins (m- 

 dusia) ; e e, capsules. C, Part of the spore-leaf of Adiantum r ,<bescens, with some 

 sori, or heaps of sporocarps, covered with reniform indusia. 



o 2 



