26 TEOPJiOLUM SPECIOSTJM. 



anticipate that it will soon be commonly grown ; and we certainly know of few 

 summer- flowering plants that more deserve the little care requisite for its 

 management. 



"We may remark, incidentally, that many of the species of Tropmolum are hardier 

 than is commonly supjiosed ; the T. tricolor, in particular, flourishes in the open 

 air in summer ; that is, when planted, as we have recommended this species to be, 

 rather deeply in the open ground, and well protected from frost and damp in 

 winter, by a heap of dry ashes, over which a hand glass or large flower pot is 

 placed. It will then grow prodigiously in the summer months, so as to be scarcely 

 recognizable by those who have been accustomed to see it only in pots. 



The genus Tropmolum is remarkable for several peculiarities which are worthy 

 a passing notice. ( Most of the species are plants of a twining habit, with delicate, 

 smooth stems, the footstalks of the leaves acting as tendrils, and twisting them- 

 selves round anything within their reach. The leaves are peltate, with radiating 

 ribs, either entire as in the common nasturtium T. majus; lobed, as in the pretty 

 annual T. pcregrinum, popularly known as the canary flower ; and cut up nearly 

 to the base into six or seven segments or leaflets, as in the present species, and 

 T. tricolor. T. polyphyllum has often ten leaflets. 



The calyx, or outer floral envelope, which, in most plants, is green and leafy, 

 is, in this family, more or less coloured, and similar in its substance to the petals, 

 forming, in many of the species, the most conspicuous portion of the flower. It 

 is in all the plants of the genus, terminated by a prolongation or spur, the length 

 of which varies considerably in the different species. Thus in the present plant, 

 in T. tricolor, T. Jarrattii, and T. Beclcerianum, it is long and slender ; whilst, in 

 T. azureum, T. tuberosum, T. polyphyllum, and T. brachyceras, it is much shorter 

 and more blunt. 



In the petals there is a considerable variation in size, from the small yellow 

 segments projecting from the calyx of T. tricolor, to the more showy ones of 

 T. azureum, and of the common nasturtium, T. majus. In T. speciosum, it will be 

 observed that the two upper petals are of a different shape to the three lower 

 ones, and are quite sessile, the others being attached to the interior of the calyx 

 by a very slender stalk or claw. 



All the plants of the order are remarkable for a certain degree of pungency, 

 similar to that existing in many genera of the Cabbage tribe, or Cniciferce, as the 

 Cress, Mustard and Eadish. This stimulating property is most observable in the 

 green fleshy fruit, but it pervades the entire plant. Dr. Candolle has remarked 

 that the identity of this principle in the two orders is attested by a curious fact, 

 viz., that the caterpillar of the cabbage-butterfly feeds exclusively upon Cruciferous 

 plants and the Tropaolums. 



The common annual, Limnanthes Douylassii, has the same pungent taste, and the 



