208 . PTIVTOTU.MV. 



Palms, Sarmentace.T, and Coronaria\ onwards to the Iri- 

 deae, Scitamineac, and Orcliidete, where it is evolved in the 

 greatest magnificence. Although these, in some respects, are 

 families of a lower rank, we yet thus see, that in the progress 

 of nature towards a more complete evohition of forms, it is 

 seldom that a harmonious construction of all the parts takes 

 place, but that commonlv one organ is exquisitely fashioned, 

 while others remain imperfect ; since the Pine tribe, the 

 ArmentaccfB and Urticea*, which, in many respects, stand 

 higher than the before named families, yet want, w ith some ex- 

 ceptions, a proper corolla, their sexual ])arts being commonly 

 protected merely by scales. 



The Polygoneae and Chenopodeae also shew only a corollar 

 integument of the calyx. In the Santale;e, Thymela^a^ 

 Proteacea^, Laurina?, and Tricocca?, the calyx is also formed 

 with the same integument, and might be mistaken for a true 

 corolla. It is in the Nyctagina^ and Primulea? that the co- 

 rolla first begins to be distinctly separated from the calvx, and 

 to take the place of a pecjuliAr organ. 



327. 



If we attend more particularly to the colour of blossoms^ 

 as their most striking characteristic, it is evident that the 

 operation of the light of the sun upon the exceedingly line 

 structure and on the juices of the delicate parenchyma of the 

 corolla, is the principal cause of the evolution of these colours. 

 This is evident from the fact, that not only tropical plants 

 have the utmost magnificence of colour in their blossoms, but 

 that also in the polar regions some very warm tints appear 

 upon the flowers ; because every person knows, that where the 

 sun does not set for several weeks, he must exert an uncom- 

 monly powerful influence on vegetation,— as is also apparent 

 from the rapid ripening of the summer crop in the polar 

 countries. 



As an internal cause of the colours of blossoms, we must 

 attend also to the green colouring matter of the leaves. The 

 tints of the blossoms arise from this, by a change in the pro- 

 portion of oxydation, as we perceive in the corollar integu- 



