IV. 



THE ANTHOCEROTES 137 



the archesporium the four primary cells of the columella divide 

 by a series of transverse walls until there are about four cells 

 in each row. Radial walls also form in the outer cells so that 

 their number also increases, and the young capsule consists of 

 the central columella composed of four rows of cells and a 

 single layer of cells outside. The archesporium now arises 

 by a series of periclinal walls in the peripheral cells of the upper 

 half only of the capsule, and is thus seen to arise from the 

 peripheral cells of the capsule, and not from the central ones. 

 Fig. 70, E shows a longitudinal section of the sporogonium at 

 this stage. Three parts may be distinguished the foot, the 

 capsule, and an intermediate zone between. The latter is 

 important, as it is from this that the meristematic part of the 

 older sporogonium is formed. With the separation of the 

 archesporium the apical growth ceases, and the future growth 

 is intercalary. 



In the capsule cell divisions proceed rapidly in all its parts. 

 The original four rows of cells forming the columella increase 

 to sixteen, which is the normal number in the fully-developed 

 sporogonium. The archesporium, by the formation of a sec- 

 ond series of periclinal walls, becomes two-layered, and the 

 wall outside the archesporium becomes about four cells thick, 

 the outermost layer forming a distinct and well-developed 

 epidermis. 



The foot grows rapidly in size, but the divisions are very 

 irregular, and finally it forms a large bulbous appendage to the 

 base of the sporogonium. The cells are large and the outer 

 ones develop still further the root-like character of those in 

 the young foot. The tissues of the thallus about the base of 

 the sporogonium 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 capsule 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. 72). The centre 



