and on Gemmation in the lower tribes of Plants. 315 



fervoid structure*, and that subsequently upon this latter are 

 produced a number of gemmae, each of which commences an 

 independent growth and quickly puts on the perfect moss-struc- 

 ture. Finally, after the moss-phyton has become fully developed 

 we still perceive the process of gemmation going on, — either by 

 the production of gemmae upon the stem, as in Aulacomnion an- 

 drogynum, Schwaegr., or upon the confervoid roots. 



In the Mosses then we find the species reproduced by a process 

 of impregnation ; — at least such seems most probable. And we 

 see the individual plant multiplied — 1st, by a subdivision of the 

 embryonic matter into a number of sporules {sporangia! gemma- 

 tion) ; 2ndly, by the production of gemmae upon the confervoid 

 filaments previously to the moss putting on its perfect form 

 (mycelial gemmation) ; and 3rdly, by gemmae being developed 

 upon the moss when in its mature state (gemmation proper). 



There can be little doubt that these same phenomena obtain 

 in many if not in most of the lower plants ; and there is every 

 reason to believe that what is frequently described as a second 

 form of fructification amongst the Algae — for instance, the tetra- 

 spores of the Floridea, the opseospermata of the Chcetophorea, 

 and the terminal " spore f" of Vaucheria — are in reality true 

 gemmae : and although it may be some time before we shall be 

 able to determine with certainty, in some of these lower forms, 

 the true character of what is usually termed fruit, yet we may 

 at once get red of the anomaly of one plant being said to pro- 

 duce two kinds of true spores ; and we shall doubtless in course 

 of time arrive at the discovery of some general laws to guide us 

 in the right discrimination of these structures. 



It is a fact well known to botanists that some species of Mosses 

 rarely if ever occur with true fructification in certain localities, 

 and the same may be said of other cryptogamous plants. As 

 instances of this kind amongst Mosses may be cited Encalypta 

 streptocarpa, Hedwig, and Trichostomum fleocicaule, B. & S. ; and 

 Parmelia physodes, Ach., and Placodium canescens, DeCand., 

 amongst Lichens. These then and many others owe their multipli- 

 cation and dispersion principally to the agency of gemmae. If we 



* Some cryptogamous plants, in this stage of their growth, exhibit so 

 close a resemblance to the mature state of other plants still lower in the 

 scale of vegetation, that without due care in watching the progress of their 

 development, they may easily be set down as distinct species. 



f The circumstance of such an organism being for a short period in its 

 earliest condition provided with mobile cilia seems scarcely to furnish an 

 argument in favour of its possessing a higher character of organization than 

 it does subsequently when these organs have disappeared. There is little 

 doubt that the motion of the cilia is due to the changes taking place within 

 the cell, and the cilia themselves are probably a mere modification of ordi- 

 nary cell-membrane. 



22* 



