SENSITIVENESS OF PLANTS. 



so insensibly the one into the other, it is impossible to show, with rigorous certainty, 

 where the one ends and the other begins. It is a curious fact that, as science is 

 extended and knowledge is increased, our difficulties arising from ignorance are 

 increased in at least an equal proportion. Years ago the definition of a plant was not 

 considered impossible ; but now he would be thought a rash man who should attempt 

 a satisfactory definition of a mineral, a plant, or an animal. This is one of the 

 evidences that knowledge was intended to humble us by showing us our ignorance. 

 The saying of Linnaeus, that minerals grow, plants grow and live, animals grow, live, 

 and feel, is now held to be an insufficient definition. The value of this terse mode of 

 expression is concealed in the assumption that the properties thus added in succession 

 do not belong in any degree to the classes preceding. Thus all three classes grow, but 

 only two live, and only one feels. This is now known to be incorrect. Thus, certain 



plants not only grow and live, but feel, 

 as in the instance of the mimosa, or 

 sensitive plant, which closes its rows of 

 leaves on a slight shock, or the Dionaca 

 muscipula, Yenus' fly-trap (Fig. 1), the 

 leaf of which folds up and incloses any 

 unhappy fly which may alight upon 

 the three hairs (A). The disposi- 

 tion of most flowers to seek or shun 

 the sunlight, and of the ears of corn in 

 the growing corn-field to droop when 

 the sun has set, might be adduced as 

 instances in proof of the sensibility, 

 apart from the mere vitality, of plants. 

 But in addition to this, it is well known 

 that the spores, or undeveloped young 

 plants of Conferva and of sea-weeds (Fig. 

 2) move about by the action of their own 

 cilia or hairs, until they have found a rest - 

 Tig. 1. DION.EA MUSCIPULA, on VENUS' FLY-TRAP, ing-place to which to attach themselves. 



A, the three sensitive hairs on the expanded leaf. Thus we may add a degree of locomo- 



B, a fly entrapped by the folding of the lobes of the ^ fo ^ qualitieg of 



and say 



that, in some instances, they grow, 



live, feel, and move. On the other hand, the sponges (Fig. 3), in their developed state, 

 are denied the faculty of 

 locomotion, although they 

 undoubtedly belong to the 

 animal kingdom. 



These characters having 

 failed to mark the distinc- 

 tion between plants and 

 animals, it has been stated 

 that an internal stomach, 

 and the chemical prin- 

 ciple called nitrogen or 

 animals only ; but this is incorrect, since the sponge has 



Fig. 2. 



Ciliated spores of the Conferva:, 

 Avhich at this stage of develop- 

 ment have u degree of locomo- 

 tion by means of the hairs or 

 cilia attached to them. 



azote, are found in 



Fig. 3. SPONGE. 



The sponge as it is found grooving 

 and attached to a rock. 



