10 HANDBOOK OF BRITISH MOSSES. 



able circumstances under which they may be placed. Some- 

 times the primary cell of the spore after the first septum is 

 formed, becomes itself septate, and gives rise to a cellular 

 nodule, and ultimately to a young plant, but more frequently 

 the new plants appear on different parts of the threads, often 

 towards the extremity of the branches or at their tips. 



Dr. Hicks, in the twenty-third volume of the ' Transactions 

 of the Linnean Society,' has described wonderful changes 

 which take place in these threads, and their conversion into 

 several genera of Al gee, besides the formation of zoospores; but 

 as he 'does not identify the species to which the observed 

 threads belonged, and the production of zoospores is a cir- 

 cumstance so extremely anomalous, we find it difficult to be- 

 lieve that he had really portions of some Moss before him, 

 and not the threads of Algse accidentally intermixed. The 

 reader can, however, refer to his paper and form his own con- 

 clusions, if he has no opportunity of testing his observations 

 by actual experiment. Some of Kiitzing's early papers may, 

 however, previously suggest some necessary caution. 



The threads arising from the germination of the spores 

 have received various names, as 'cotyledonoids,' 'protonemata,' 

 ' proembryo,' ' prothallus.' The first of these is objectionable 

 because they have no analogy with true cotyledons, and the 

 third because an intermediate stage must take place before 

 the cell capable of impregnation is produced in the archegon, 

 the result of which, after all, is a sporangium and not an em- 

 bryo. The production of the plant from the threads is rather 

 gemmiparous than embryonic, and I therefore strongly object 

 to the term ' proembryo,' which inevitably more or less directly 

 leads to confusion. The second name at least is free from 

 error, and if the Moss plant may be called a ' thallus,' the 

 fourth name may be admitted. If new terms were not ob- 



