544 ORGANOLOGY. 



Euphorbia phosphorea (Martius, Reise nach Brasilien, vol. ii. pp. 726 and 

 746), belongs to physical and not botanical science. 



C. Movements of the Parts of Plants. 



213. Two kinds of motions of the parts of plants can be dis- 

 tinguished : 1st, those that are produced in the dead parts of plants 

 by the change from the moist and dry state ( 214.); and, 2dly, 

 those which are caused in a manner as yet unknown to us, by 

 changes in living cellular tissues ( 215.). 



A third kind of so-called movement, which does not belong here, 

 brings a phenomenon of growth which determines the direction of 

 certain parts, as the peculiar form of tendrils and the growth of the 

 climbing plants. 



Finally, those movements must be mentioned which entire plants 

 are said to exhibit, as the OscillatoricR and some other forms of the 

 lower Algce( 215.). 



The third form of phenomena alluded to above does not belong to true 

 movements, although many consider them as such. It depends on the di- 

 rection (the same takes place in the germinating plant when it is growing 

 towards the light) given by an unequal tension of the cells on both sides, 

 whereby that side is curved in which the cells grow least in the longitu- 

 dinal direction. Similar irregularities occur, not unfrequently, in the 

 extension of plants, but without producing any remarkable departure from 

 their normal condition. They only create a tension, the effect of which 

 only becomes visible when the continuity of the parts is interrupted by an 

 accident. We may mention, as belonging to the same phenomena, the 

 sudden curvature which particular parts of plants occasionally exhibit, as, 

 for instance, the hollow flower-stalk of Leontodon Taraxacum, when it is 

 split, or when a longitudinal strip is cut out of it, &c. 



214. The first kind of movements are either perfectly ex- 

 plainable, or, if not, it is owing to our inaccurate knowledge of the 

 structural relations and other elements that demand attention, as 

 the causes, remaining always the same, are known to us. All the 

 phenomena under this head take place in the organs of plants, the 

 elementary parts of which are either already dead or in the act of 

 dying, but all of which are still of importance to the entire life of 

 the plant ; all, finally, are more or less connected with its reproduc- 

 tion by facilitating changes in the locality of the reproductive cells 

 (spores or pollen-grains) or of the seed. We find phenomena 

 of this description in almost all groups of plants. To such belong 

 the valvular bursting of the species of Geastrum and some other 

 Fungi, the opening of the spore-fruits, the movements of the teeth 

 and the seta in Mosses, the bursting of the spore-fruits in the 

 Liverworts, the tearing open of the same in Ferns, Lycopodiacece, 

 and EquisetacecB, the bursting of the anthers of the capsules, and the 

 loosening of some parts of the fruit mEuphorbiacecB, 



