TRUCTURE.] MR. THWAITES'S VIEWS. 113 



extremities, and at length a bud containing the rudiments of 

 stem, leaves, and roots is formed, which may be considered 

 analogous to the embryo or young bud, in the seed of more 

 highly organised plants." (Linn, Trans, vol. xvii.) 



Mr. Thwaites, however, supports the sexuality of the an- 

 therids and pistillids of Mosses on new grounds, and with so 

 much skill that we should leave the subject very incomplete 

 if we did not give his ingenious views nearly in his own words. 

 After observing that he thinks it probable that the conjugation 

 of Brittleworts will throw light upon the real nature of 

 the so called antheridia and pistillidia (archegonia] of Mosses, 

 he proceeds thus: "The paper on this subject by Mr. 

 Valentine would seem to settle the point that there can be no 

 impregnation of the contents of the moss-capsule by the 

 introduction into its cavity of any external substance, after 

 the formation of the sporules. On the other hand, the 

 learned authors of the Bryologia Europeea state with 

 emphasis that certain species of Mosses, which are dioecious, 

 that is, some plants of the same species bearing anthe- 

 ridia only, and others only archegonia, 'do not bear fruit 

 unless the male plants (those with antheridia) are in the 

 neighbourhood of the plants possessing archegonia. It 

 is perhaps not impossible to reconcile these, at first sight, 

 apparently conflicting opinions. It may be that impregna- 

 tion takes place before the production of the capsule ; that 

 the cell from which the capsule, with its seta, &c., is de- 

 veloped corresponds with the sporangium of the Diatoma- 

 ceous plant, or the embryonic cell of the flowering plants ; 

 that this cell contains a mixed endochrome derived partly 

 from the antheridia; and that the entire capsule (with its 

 contents, appendages, &c.), the further development of this 

 primordial cell, corresponds to a perfect seed of the flowering 

 plant, or to the aggregate of the sporangial frustules of a 

 Diatomaceous plant. It is true that in some of the Mosses 

 the structure of the capsule appears very complicated, but it 

 is upon a very simple type, as shown in other species ; and, 

 moreover, the sporangial frustules of the Diatomaceous plant 

 possess cell-walls as highly developed as occur in any other 

 phase of the species. In some of the Conjugate there is 



VOL. II. I 



