1 82 MOSSES AND FERNS chap. 



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. 85, 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 

 gametophore the first rhizoid (Fig. 85, 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. 85, 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.^ Amblystegium 

 riparium, var, fluitans, was examined by me and differed in 

 some points from Leitgeb's figures of Fontinalis. Fig. 86, 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 



^ Leitgeb (i). 



