36 



FISSIDENS B MYOID ES. 



The same as in Ceratodon, all attempts to grow proto- 

 iiema from the leaves of Fissidens were ineffectual. The 

 leaves were kept for three months and at the end of that 

 time, although in apparent vigor, no protonema had been 

 produced. The stems, when stripped of leaves, produced 

 rhizoids direct from the region of the leaf axils in both 

 light and darkness. In the light howerer the rhizoids soon 

 grew to possess a distinct protonema character, but no proto- 

 nema originated direct from the stem. The stems grown 

 in the dark produced long, sparcely branched rhizoids, which 

 attained a length of about 1 cm after a raonth of growth. 

 When first examined they possessed only oblique cross-walls, 

 but at this time nearly all showed alternately oblique and 

 perpendicular walls. The oblique walls were the ones first 

 formed and the perpendicular walls were produced later by 

 intercalary division. The great regularity of the alternately 

 oblique and perpendicular cross-walls was due to the fact 

 that each cell had become divided by a perpendicular wall. 

 This fact is mentioned since intercalary division is an ex- 

 ception to the usual mode of protonema and rhizoid growth, 

 and since it affords another example of perpendicular cross 

 walls being produced in darkness. 



No buds were produced from the protonema grown from 

 the stem, but the stem gave rise to buds, and that in a 

 peculiar way. After one month of culture the stems grown 

 in the light were found to have produced buds direct from 

 the region of the leaf axils, without the Intervention of any 

 protonema. A bud grown in this way is shown in Fig. 53. 

 A surface cell from the region of the leaf axil produces a 

 protuberance , which instead of growing out into a rhizoid 

 or protonema divides directly to form a bud. This manner 

 of bud formation was observed only in light cultures. Plants 

 with the leaves still in tact, also produced buds in the same 

 way although not in as great abundance as in the defoliated 

 stems. The buds were in the course of time detached from 



