XXVI INTRODUCTIOX. 



calyx is the real origin. Upon this supposition, what is now called 

 the tube of the calyx may be sometimes a peculiar extension or 

 hollowing; out of the apex of the pedicel, of which we see an example 

 in Eschscholtzia, and of which Rosa and Calycanthus, and perhaps 

 all supposed tubes without apparent veins, may also be instances. 

 In this case the whole of our ideas about superior and inferior 

 calyxes will require modification. But upon this subject I cannot 

 enter here : I have in the following Work spoken of these points of 

 structure according to the received opinions of botanists. 



The second floral envelope we call the Corolla. It consists of 

 a number of leaves equal to those of the calyx, and alternating with 

 them ; in addition to which they are usually coloured. — If the corolla 

 is present, a plant is said to be dichlamydeous, and much importance 

 is attached to this peculiarity ; far more, I think, than it deserves. 

 It constantly separates plants having much natural affinity, as 

 Euphorbiacese far from Rhamnese, Amarantacea widely from Illece- 

 breee ; and it is also one to which there are numberless exceptions. 

 This is, however, not the case with monopetalous dicotyledons, 

 Primulacese and Oleaceae being almost the only instances of orders 

 among those which are truly monopetalous, containing apetalous 

 genera. — The difference between a monopetalous and a polypetalous 

 corolla is this, that in the one the leaves out of which the corolla is 

 formed are distinct, and in the other united. Great value is at- 

 tached to this, and it is in fact a difference of first-rate importance : 

 thus, all Ranunculaceae, Rosaceae, Cruciferae, Papaveracea, Tere- 

 bintaceae, and a multitude of others, are, without exception, poly- 

 petalous ; and all Boragineae, Labiatae, Scrophularineae, and Big- 

 noniaceae, are equally, w^ithout exception, monopetalous: but in the 

 polypetalous orders of Crassulaceae, Diosmese, Polygaleae, Ternstrci- 

 miaceae, &,c., there are many monopetalous genera ; and monopetalous 

 Caprifoliaceae are usually associated with Hedera and Cornus, which 

 are as much polypetalous as any other plants. — The aestivation of 

 the corolla rarely furnishes characters connected with the natural 

 properties of plants ; nevertheless, Compositae are essentially dis- 

 tino-uished by their valvate, and Asclepiadeac and Apocyneae by their 

 contorted aestivation, an exception to the one existing only in the 

 genus Leptadenia, and in the other in Gardneria. The aestivation 

 of both calyx and corolla has as yet received too little attention 

 for its value to be judged of generally. — The regularity or irregu- 

 larity of the corolla is most commonly important: thus, Orchideae, 

 Polygaleae, Bignoniaceae, Fumariaceac, are irregular without ex- 

 ception ; the regular flowers of Boragineae will almost distin- 

 guish them from Labiatae, which have as frequently irregular ones; 

 yet Echium in Boraginea} is irregular, and Caprifoliacco; exhibit 



