258 MOSSES AND FERNS CHAP. 



then ceases to grow. This root appears to be formed directly 

 from the main root, and as the latter continues to grow the effect 

 is that of a true dichotomy. The latter does occur, but not 

 frequently. 



The formation of adventitious buds upon the roots is the 

 principal method of propagation of some species of Ophioglos- 

 sum, whose prothallia, as we have seen, are apparently very 

 seldom developed. Rostowzew states that these are not de- 

 veloped from the apical cell of the root, but arise from one of 

 the younger segments, and the apical cell of the bud is produced 

 from one of the outer cells of the young segment, but is covered 

 by the root-cap, through which the bud afterwards breaks. 

 The sheath covering the first leaf of the bud is formed from the 

 cortex of the root and the root-cap. 



Differing most widely from the other species in general 

 appearance is the curious epiphytic 0. (Cheiroglossa) palma- 

 tum. In this species the leaf is dichotomously branched, and 

 instead of a single sporangiophore there are a number arranged 

 in two rows along the sides of the upper part of the petiole and 

 the base of the lamina. 



According to Bitter ( ( i ) p. 468), O. pendulum also has the 

 sterile leaf segment dichotomously divided, but this was never 

 the case in the specimens collected by the writer in various parts 

 of the Hawaiian Islands. These invariably had an undivided, 

 strap-shaped leaf. 



In 0. Bergianum the plant is very small and the sporangia 

 are reduced in number to a dozen or less. The sterile segment 

 is inserted very far down. A most remarkable form has been 

 recently described from Sumatra (Bower (20) ). This species, 

 O. simplex, is described as having no sterile leaf-segment, or the 

 merest rudiment of one, the sporophyll being a flattened slender 

 body, with the sporangia closely resembling those of O. pen- 

 dulum, to which 0. simplex seems to be allied. O. simplex 

 may be considered to represent the most primitive type of the 

 genus yet discovered. 



BOTRYCHIUM 



The genus Botrychlum includes several exceedingly variable 

 species, the simplest forms, like B. simplex (Fig. 141, A, B), 

 being very close to Ophioglossum, while leading from these is a 



