286 



GENERAL REMARKS. 



dicles have a great tendency to run towards the central 

 vein, along which they for the most part strike root exclu- 

 sively, although, as might be expected, they do not originate 

 from the vein itself. It is a curious fact, that those of the 

 fructiferous portions of fronds, do not generally strike root un- 

 til they have arrived at that portion of the frond, from which 

 the fructiferous part was developed. And it will be seen that 

 in obedience to this tendency, curious means are in many 

 species contrived for conducting them to this point. 



In their younger states they contain numerous active mole- 

 cular granules, but I have not been able to ascertain that 

 these are subjected to any circulation. 



These granules disappear as the radicles lengthen, and are 

 subsequenly not to be met with, This may be considered 

 as corroborative of Mr. Brown's suggestion concerning the 

 nutrient functions of the granules contained in the pollen 

 tubes. 



With regard to the foliaceous species which are confined 

 to Jungermannia, of which genus they form by far the larger 

 portion, it appears to me that the authors who have studied the 

 genus have mistaken its structure. I am unable at present to 

 state whether there are material objections against considering 

 these species as the result of the maximum division of the 

 frondose forms. My ideas of the structure will be found under 

 the genus. I shall here only point out in addition, that 

 the ampullaceous lobes, which are evidently due to cohesion 

 of the margins of concave lobes, become again expanded in 

 the leaves surrounding the organs of both sexes. 



The receptacula of authors are in all cases, except in Aso- 

 lenium, to be considered as modified portions of the frond, 

 the peduncle being a continuation of the central vein, and 

 its overlying structures. This portion will hence, always 

 correspond to the sinus of the emargination of the lobes of 

 the fronds, from which it is indeed almost universally exserted. 

 And it will hence as obviously follow, that both peduncle and 

 receptacle will have the exact structure of the portions of the 

 frond to which they correspond. 



