CRYPTOGAMOUS PLANTS. 257 



out either by the destruction of the tissue ( Ulva), or by 

 regular pre-existing pores ( Fucus). 



In all these plants it frequently happens that the 

 spores germinate in the sporangia, or in the cavities 

 which contain these bodies ; this we can easily see by 

 the naked eye. 



§ 3. — Confervas. 



The Conferva) (I use this term here in the sense in 

 which Vaucher has employed it) all grow in fresh water. 

 Notwithstanding their external resemblances, they pre- 

 sent great differences in their reproduction, which I 

 shall rapidly point out, taking for my guide the excellent 

 work of Vaucher (ll'tstoire des Conferves d'eau douce). 



The Vaucheriae, or Ectospermae of Vaucher, present, 

 at the period of fructification, sessile pedicellate tuber- 

 cles, solitary or in pairs, or sometimes collected several 

 together upon a peduncle. These bodies separate natu- 

 rally from the plant, and Vaucher has seen them ger- 

 minate : at this period they usually shoot out a green 

 filament like the plant which has given birth to them ; 

 more seldom another filament proceeds from the oppo- 

 site side. The body is not seen to open for the de- 

 velopment of these filaments, so that we may as well 

 consider them to be bulbs as seeds. Vaucher has also 

 observed in most species of this genus little clubs or 

 hooks, from which he has seen a fine greenish powder 

 proceed : he considers them as male organs. 



The Zygnemse present a much more complicated 

 organization. At the period of their fructification, their 

 filaments approach one another by pairs ; from one 

 filament to the other there are kinds of hollow tubercles, 



vol. II. s 



