92 COMPOUND ORGANS OP PLANTS. 



resting facts revealed by geologists prove that the mutable 

 and perpetually changing system of wonders by which we are 

 surrounded is under the control of a sublime and mysterious 

 Providence. 



136. We have seen that every plant which consists of 

 more than one cell or of a series of cells, which are permanently 

 united together, may be divided into two distinct parts, to 

 which the functions of nutrition and reproduction are respect- 

 ively assigned (54). In like manner, all the organs which 

 compose the structure of the most highly organized vegeta- 

 tion concur in the exercise of either one or other of these 

 functions. In the compound organs of plants, we have addi- 

 tional complexity of structure, but no essential change of 

 plan. The same distinction may be made of them into 

 organs of vegetation and reproduction. 



137. In the lower orders of the cryptogamia or flowerless 

 plants, the organic parts which concur in the exercise of these 

 functions are reduced to the utmost degree of structural 

 simplicity, being at first confined to a single cell, as exempli- 

 fied in the Protococcus, and certain confervoid plants (51), 

 in which the union of the plant-cells is but temporary. But, 

 as we advance in the scale of vegetable organization, we find 

 these plant-cells remaining permanently united to each other, 

 and developing into filamentous or foliaceous expansions, and 

 finally into distinct organic parts, designated as root, stem, 

 and leaves : so also the reproductive matter is at first confined 

 to the same vegetative cell, then concentrated in certain special- 

 ized cells as in the bread-mould, and finally contained in regular 



