432 MOSSES AND FERNS chap. 



of the exact origin of the primary meristem and its relation to 

 the secondary ones found in the branches is much to be 

 desired. 



Each archegonium stands between two lobes, the one from 

 whose base it has itself developed, and the next younger one. 

 As these lobes in vigorous prothallia grow to a large size, and 

 branch, this gives the prothallium an extremely irregular out- 

 line, recalling very much that of Anthoceros punctatus or A. 

 fusiformis. These branching lobes are not to be confounded 

 with the branches of the prothallium body due to the dichotomy 

 of the archegonial meristem. These latter are always short, 

 and project but little compared to the secondary branching 

 lobes produced from them. The entrance of the spermatozoids 

 and the changes subsequent to fertilisation seem to be exactly 

 the same as in Ferns. 



The prothallia are normally dioecious, but this is not 

 exclusively the case. To a certain extent the external con- 

 ditions influence the production of males or females, as in the 

 Ferns, and unfavourable conditions of nutrition tend to increase 

 the proportion of the former. 



According to Hofmeister ^ the number of archegonia upon 

 vigorous prothallia varies from twenty to thirty. His statement 

 that this exceeds the number of antheridia in the larger male 

 prothallia is not confirmed by Buchtien,""^ who found as many 

 as I 20 of the latter in some cases. 



Usually more than one archegonium is fertilised, Hofmeister 

 having found as many as seven embryos upon a single pro- 

 thallium. He does not state how many of these develop. 

 The embryo corresponds closely to that of the Ferns, and has 

 been carefully described by Sadebeck.^ 



TJie Embryo 



The fertilised ^'g'g grows until it completely fills the ventral 

 cavity, and its granular contents become more separated, and 

 the nucleus is decidedly larger than before fertilisation. The 

 lower neck cells approach and apparently become grown 

 together, and as the divisions in the lower neck cells here 

 contribute to the calyptra, the young embryo becomes more 



^ Hofmeister (i), p. 301. - Buchtien (i), p. 22. 



"' Sadebeck ; Pringsheim's "Jahrb. fiir wiss. Botanik," 1878. 



