272 BIOLOGY. 



possible if the plant were an organism disengaged from 

 the elements ; but as the earth and air belong to its 

 organization ; it thus necessarily oscillates between both, 

 and its movements also can only be oscillations of a similar 

 intervening character. 



1449. There are consequently no arteries and veins, 

 and still less a heart in plants, as some have striven to 

 make out. 



1450. The vessels of plants are most properly to be 

 compared with the lymphatic vessels of animals, the 

 fluid or sap of which also tends from all parts towards 

 one summit, namely, the lungs, while still at times retro- 

 gressive movements also seem to occur. 



1451. The vegetable sap does not move in a straight 

 line upwards, but in all directions, to the right and left, 

 in a zigzag manner, and so on. This is proved by two 

 incisions being made in a branch opposite to each other. 

 The motion of the sap in the plant is more an impulsion 

 of the sap toward all sides, with a predominance in the 

 direction upwards, than a rapid current as in the blood. 

 If we reflect that the motion of the sap when seen under 

 the microscope and then magnified several hundred times, 

 still only resembles a gentle rippling of small drops, it 

 thus becomes clear that the true current or flow occurs 

 only in a very tardy manner. Wherever therefore in 

 the plant the process of differencialization may be brought 

 into play, there the sap is impelled. 



1452. Through the polarization of the sap the cells 

 also become polar towards each other, and then even the 

 cell-walls, whereby the cellular sap with its mucous 

 granules is kept in constant motion. The theory of the 

 motion of sap has not consequently been based upon the 

 theory of capillary tubules ; nor is heat alone the cause 

 of its ascent; nor the empty space, which originates su- 

 periorly by evaporation ; nor electricity in an inorganic 

 sense. 



II. FUNCTIONS OF THE FLORAL-ORGANS. 



1453. These functions correspond to those of the light, 



