190 MOSSES AND FERNS chap. 



After the cell is separated it is usually divided at once by a 

 strongly oblique wall, which is then intersected by two others 

 successively formed and meeting each other and the first-formed 

 one at nearly equal angles, so that the terminal cell of the young- 

 bud (Fig. 97, A), has the form of an inverted pyramid; that 

 is, by the first divisions in the bud the characteristic tetrahedral 

 apical cell of the gametophore is established. From now on 

 the apical cell divides with perfect regularity, cutting off three 

 sets of lateral segments. From the base of the young gameto- 

 phore the first rhizoid (Fig. 97, A, r), is formed at a very early 

 period. The first two or three segments do not give rise to 

 leaves, and the leaves formed from the next younger segments 

 remain imperfect. Thus in Funaria hygrometrica these earliest 

 formed leaves show no midrib. The young leaves rapidly 

 elongate and completely cover up the growing point of the 

 young bud, and are at first closely imbricated. Later, by the 

 elongation of the axis, the leaves become more or less completely 

 separated (Fig. 97, C, D). In Funaria, as well as in many 

 other Mosses, buds are often met with that have become arrested 

 in their development, lost their chlorophyll, and assumed a dark- 

 brown colour. This arrest often seems to be the result of un- 

 favourable conditions of growth, and under proper conditions 

 these buds probably always will develop either directly or by 

 the formation of a secondary protonema into perfect plants. 



Apical Growth of the Stem 



The growth of the stem of the fully-developed gametophore 

 is better studied in one of the larger Mosses. The growth of 

 the gametophore is so limited in length in Funaria that it is 

 not so well adapted for this. Perhaps the best species for this 

 purpose is the well-known Fontinalis antipyretica, which has 

 already been carefully studied by Leitgeb ( i ) . Amblystegium 

 riparium, var. Uuitans, was examined by me and dififered in 

 some points from Leitgeb' s figures of Fontinalis. Fig. 98, A 

 shows an exactly median longitudinal section through a strong 

 growing point. Compared with Leitgeb's figures the apical cell 

 is much deeper than in Fontinalis, and in consequence the young 

 segments more nearly vertical. Here, as in Sphagnum, the first 

 wall in the young segment divides it into an inner and an outer 

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



