FUNCTION.] ACANTHADS, FLOWERS. 149 



That it is in this sense that Professor Morren is to be under- 

 stood is evident from the manner in which he endeavours to 

 explain the singular vital actions observable in the irritable 

 stigma of some Acanthads, &c. "The movement of the 

 style of the Goldfussia had escaped the investigation of 

 naturalists ; it is notwithstanding very remarkable. Most of 

 the flowers in which we see a moveable pistil possess a bilabiate 

 stigma; here the moveable part is awl-shaped and rather 

 spindle-shaped. The true stigma occupies only the dorsal 

 part of the style, and when it bends back it removes as far 

 as possible from the stamina; when it again erects itself it 

 comes in contact with collecting hairs, which from the posi- 

 tion of the flower, or by the help of insects, receive the 

 pollen. The final cause of the phenomenon is very certainly 

 the accomplishment of fecundation; but the mechanical 

 cause is seated in the distension of the cylindrenchym of 

 the stigma ; its tissue is formed by long cylinders dilatable at 

 one or other of the extremities, and each is filled with a 

 liquid containing globules. These globules are excitable. 

 They are naturally carried towards the outer extremities of 

 the cylindrenchym, and then these extremities dilating, 

 make the stigma bend ; but when it is touched the globules 

 and the liquid flow back to the bottom of the cylinders, and 

 in this case, this side becoming the longest, the style erects 

 or bends itself in a direction the reverse of that which it had 

 before. The physiological cause resides therefore in the 

 excitability of a vital fluid." 



It is indeed impossible to explain any one phenomenon of 

 life in plants upon any other supposition. Let us take the 

 commonest cases. The flowers of the Crocus and similar 

 plants expand beneath the bright beams of the sun, but close 

 as soon as they are withdrawn. The (Enotheras unfold their 

 blossoms to the dews of evening, and wither away at the 

 approach of day. Some Silenes roll up their petals in the 

 day, and expand them at night. The florets of numerous 

 Composites, and the petals of Mesembryanthemum, are erect 

 in the absence of sun, but become reflexed when acted upon 

 by the sun's beams ; and many other such phenomena are 

 familiar to every observer of nature. It is probable, indeed, 



