22 ORGANS OF PLANTS. 



The. nourishment of plants. Being deprived of the powers of 

 locomotion, plants must have organs to obtain their food from the 

 situation in which they are placed, and also for assimilating it. This 

 food is in a liquid or aeriform state. The solid particles held in liquids 

 must be in a very fine state, as commonly diffused in water or rain. 

 When placed in water, plants bloom, but the nourishment of the water 

 is soon exhausted. Distilled water has lost that nourishment, or its 

 carbonic acid gas, etc., and plants soon die in it. 



Sponglets or suckers, like the organs of insects that live by suction, 

 are minute sponge-like vessels, on the point of the rootlets, radicles, 

 or small fibres. These pores admit only of fine particles dissolved in 

 water, otherwise they become obstructed and the plant perishes. The 

 pores or suckers of leaves are similar, and perform similar functions. 



The. sap vessels are congeries of fine tubes, straight and curved, 

 forming lace-work, or they are of a beautiful spiral form. The. 

 straight vessels are hollow threadlets, fifty times finer than a hair, and 

 forming, together, large tubes. The spiral vessels act singly or in bun- 

 dles in every part of the plant, except the bark. The circulation through 

 these, upwards and downwards, is elsewhere alluded to. The organs 

 of aeration are not like those of the lungs, any more than the pith in 

 the cirulation is like the heart of animals ; yet analogous functions are 

 performed by them in both. They breathe, and it is by the air they are 

 chiefly nourished, as will be seen in another place. 



Organs of sensation in plants. It has been thought by some that 

 plants are endowed with sensation, sentiments and propensities. Ner- 

 vous organs have been disclosed, it is said, in the sensitive and other 

 plants. There is at the base of the leaf-stalk of this plant, a swelling 

 collar constituted of a delicate tissue of cells, on which the motion of 

 the leaves depend. The under part being cut away, the leaf bends 

 down and cannot again rise, and the upper part being cut, it cannot 

 bend. These are acted on, it is believed, by nervous globules, or 

 grains or ganglia, as diffused in all plants by medulary vessels. The 

 effects of experiments certainly show an analogy between plants and 

 animals. Leaves and flowers turn to the light when twisted ; these 

 curl up and die when watered with poisons. Twining plants twine 

 from right to left or left to right, according to species. 



The existence of plants has been compared to that of animals when 

 asleep, their functions proceeding during the time without conscious- 

 ness. A seed placed in the earth is similar in its nature to the egg 

 of an animal, and the effects of the earth would seem not unlike that of 

 sitting upon it, or the development of the young of amphibious animals 

 with the egg covered by the earth. It is obviously very difficult to 

 determine at what point vegetable life ends and animal life begins. 

 The sponge is in many respects less sensible than some plants, yet 



