VII 



THE BRYINE^ 



i8^ 



cell, from the latter of which alone are formed the lateral 

 appendages of the stem. The inner cells of the segments by 

 repeated longitudinal and transverse divisions form all the tissues 

 of the axis. The second division wall in the segment, like that 

 in SpJiagmnn, is at right angles to the first, but in Aviblystegmvi 

 it extends the whole breadth of the segment. By this division 

 the outer of the two primary cells of the segment is divided 

 into an upper cell, from which the leaf develops, and a lower 

 one, from which the outer part of the stem and the buds are 



Fig. 85. — Aiiiblystegiitin ripariiuii, var.Jiuitaus {Yir\xc\is.nA Schimp). A, Median longitudinal section 

 of a strong shoot ; .v, apical cell ; .r', initial of a lateral branch, X 250 ; B, transverse section 

 through the apex, X 250 ; C, similar section through a young branch, X 500. 



formed. The leaves grow from a two-sided apical cell (Fig. 87), 

 as indeed they seem to do in all Mosses, and the divisions pro- 

 ceed with great rapidity and the young leaves quickly grow 

 beyond and surround the growing point. In Aniblystegmm, as 

 in all the typical Bryineae, the leaf has a well-developed midrib. 

 The formation of this begins while the leaf is very young and 

 proceeds from the base. In the middle row of cells (Fig. 87, C) 

 a wall first arises parallel to the surface of the leaf, and this is 

 followed by a wall in the cell on the lower side of the leaf 



