INTRODUCTION. 19 



once an increase of three-twentietlis of a millemetre in an 

 hour. Moreover, the activity of this phenomenon, as of all 

 those which I shall hereafter describe, varies extremely, 

 according to the state of tlie tufts of Vaucheria Avhich have 

 been gathered. It is the same with the diameter of the spores, 

 and the size of the filaments, &c., upon Avliich one is not able to 

 give a certain determination. Therefore, in the figures which 

 I append to this note, all the modifications wdiich the spores 

 of Vaucheria may present, either before or after their emis- 

 sion, ought not to be expected to be found; but I have 

 chosen in my drawings those wliich have appeared to me to 

 represent their most usual and characteristic state. 



The power of germination is moreover carried in Vaucheria 

 to a point which appears to me to surpass all that is observed 

 in the vegetable kingdom. This plant, which consists, to 

 speak truly, but of a single cell, possesses in all its parts the 

 faculty of reproducing itself. The extremities of the fila- 

 ments kept for many weeks, evaporation being prevented, 

 continue to elongate until they have extended them- 

 selves beyond the plate of glass which serves to sustain 

 them. Again, when one of these filaments has undergone 

 lesions in many places, the green matter is seen to become 

 secreted gradually between one end of the injured j^laces and 

 the filament, and to divide itself thus into many little 

 fragments, Avhich form so many distinct individuals emitting 

 lateral prolongations, and not tarrying, without doubt, under 

 favourable circumstances, to reproduce a complete individual. 



The phenomenon of the deliverance of the spore is not always 

 accomplished so regularly as I have described ; sometimes it 

 germinates without quitting the mother plant ; and from this 

 result the strange forms which I have represented iu figures 

 35 and 36. Sometimes also the spore cuts itself into two 

 at the moment of its escape, and so gives birth to two spores, 

 smaller than the others, but capable of germination like 

 them, the one at the exterior, the other at the interior, of the 

 filament. 



The transparent membrane which enclosed the spore, and 

 which became visible after its emission, is destroyed little 



