THE ANTHOCEROTE/E 



I SI 



pendage to the base of the sporogonium. The cells are 

 large and the outer ones develop still further the root-like char- 

 acter of those in the young foot. The tissues of the thallus 

 about the base of the sporogoiiiuni grow rapidly with it, and 

 the connection between the surface cells of the sporogonium 

 foot and the adjacent cells of the thallus is very intimate. 



The subsequent growth of the cap- 

 sule is entirely dependent upon the 

 activity of the zone of meristem at 

 its base. This divides very actively, 

 and the divisions correspond exactly 

 with the primary ones in the young 

 embryo, so that the completed portions 

 of the older parts of the capsule are 

 continuous with the forming tissues at 

 the base. A series of cross-sections at 

 different points, compared with a median 

 longitudinal section, shows in a most 

 instructive way the gradual development 

 of the different parts of the mature 

 capsule (Fig. 62). The centre of the 

 sporogonium is occupied by a colu- 

 mella composed of sixteen rows of cells, 

 which in cross-section form a nearly 

 perfect square. At the base these cells 

 are thin -walled and show no intercell- 

 ular spaces, but farther up their walls 

 begin to thicken and the rows gradually 

 separate until in the upper part the 

 columella has somewhat the appearance 

 of a bundle of isolated fibres. The 

 archesporium is constantly growing from 

 below, and the new cells are cut off 

 from those surrounding the columella in the same way as at 

 first. The archesporium, as well as the columella, can be 

 traced down nearly to the base of the capsule, and its cells are 

 very early recognisable both by their position and by their 

 contents. At first but one cell thick, the archesporium soon 

 becomes double, but does not advance beyond this condition. 

 As the archesporium is followed from the base towards the 

 apex of the capsule the cells begin to show a differentiation. 



Fig. 61. — Anthoceros la-cis (L.)- 

 Median longitudinal section 

 through the base of the sporo- 

 gonium. The archesporium is 

 shaded. F, Foot ; v, v, basal 

 sheath, x loo. 



