SECTION IC] 



MOVEMENTS. 



149 



they restore an equal bulk of life-sustaiuing oxygen needful forthe respiration 

 of auiaials, — needful, also, in a certain measure, for plants in any work they 

 do. For in plants, as well as in animals, work is done at a certain cost. 



§ 6. PLANT WORK AND MOVEMENT. 



458. As tlie organic basis and truly living material of plants is identical 

 with that of animals, so is the life at bottom essentially the same ; but in 

 animals something is added at every rise from the lowest to highest organ- 

 isms. Action and work in living behigs require movement. 



459. Living things move ; those not living are only moved. Plants 

 move as truly as do animals. The latter, nourished as they are upon or- 

 ganized food, which has been prepared for them by plants, and is found 

 only here and there, must needs have the power of going after it, of collect- 

 ing it, or at least of taking it in ; which requires them to make spontaneous 

 movements. But ordinary plants, with their wide-spread surface, always 

 in contact with the earth and air on which they feed, — the latter every- 

 where the same, and the former very mucli so, — might be thought to liave 

 no need of movement. Ordinary plants, indeed, have no locomotion; some 

 float, but most are rooted to the spot where tliey grew. Yet probably all 

 of them execute various movements which must be as truly self-caused as 

 are those of the lower grades of animals, — movements which are over- 

 looked only because too slow to be directly observed. Neveitheless, the 

 motion of the hour-hand and of the minute-hand of a watch is not less real 

 than tliat of the second-hiaid. 



460. Locomotion, iloreover, many microscopic plants living in water 

 are seen to move freely, if not briskly, under the microscope ; and so like- 

 wise do more conspicuous 

 aquatic plants in their embryo- 

 like or seedling state. Even at 

 maturity, species of Oscillaria 

 (such as in Fig. 4S8, minute 

 worm-shaped plants of fresh , ^ 

 waters, taking this name from -<5^m£rf55^ 

 their oscillating motions) freely 488 



execute three different kinds 



of movement, the very delicate investing coat of cellulose not impeding the 

 action of the living protoplasm within. Even when this coat is firmer and 

 hardened with a siliceous deposit, such crescent-shapod or boat-shnped 

 one-celled plants as Closterium or Ndtncula are able in some way to move 

 along fro;)i jilace to [ilace in the water. 



4G1. Movements in Cells, or Cell-circulation, sometimes called Cy- 

 closis, has been dit.-ctcd in so many plants, especially in comparatively 



Fig. iSS. Two iudiviJuals of au Oscillaria, magnitied. 



