ORGANOGRAPHY. 



Fig. 438. 



Fig. 438. Flower of the White Water-Lily iNympliCPa alha) reduced in size. 

 After Jiissieu. c, r, c, c. The four sepals. j9./>,y/, />. Petals, e. Stamens. 

 The parts on the right show the gradual transition from the calyx c to 

 the petals^j, and from those organs again to the stamens e. The stamens 

 from 1 to 5 are gradually more distinctive. 



corolla, or of some other. In such cases it is said to be petaloidj 

 and the chief distinctive character between it and the corolla is 

 then afforded by its position on the outside of the latter organ. 

 The Fuchsia, Indian Cress, Columbine, Larkspur, and Monks- 

 hood, may be mentioned as affording us examples of a ])etaloid 

 calyx among Dicotyledonous Plants. In the Monocotylcdonous 

 Plants generally, as in the Lily, Iris, Tulip, Crocus, &c. {Jig. 

 424), as we have mentioned, the two floral envelopes are usually 

 coloured, and in other respects closely resembling each other, 

 so that we then use the collective name of perianth to indicate 

 the two whorls taken together. When tliere is but one 

 whorl of floral envelopes, as in the Goosefoot (Chenopodium) 

 (^fig. 425), and in Birtliwort (Aristolochia), it is customary 

 with some botanists to call that whorl a calyx, whatever be its 

 colour or other peculiarity. It is so termed in this volume. 

 Otlicr botanists, however, frequently term it a perianth under 

 such circumstances, as we have already stated. (See p. 216.) 



In their general structure, venation, &c., the sepals resemble 

 true leaves, and are covered like them with ei)idcrmis, and this 

 is frequently furnished on the lower and outer surface with sto- 

 mata, and also occasionally with hairs, glands, and other appeiul- 

 ngcs. From their duration being usually however more transi- 

 tory than that of true leaves, the veins which form their skeleton 

 chiefly consist of true spiral vessels, which arc arranged like 

 those of tl^e leaves in the two classes of plants — that is reticu- 

 lated in Dicotyledons, and i)arallel in Monocotyledons. 



The 8ci)als also cxhil>it various characters as regards their 

 outline, apex, &c., although by no means so liable to variations 



