ANALOGY OF PLANT OEGANS. 61 



the true leaf-blades are also sessile imraediatcly below the flower, 

 aud the veiuitiou in the yellow sepals is palmate and dicliotoinous, 

 as in the leaf-blades. In Udlehorus the venation of the sepals is 

 higldy anastomosed but palmate, whereas it is pinnate in the true 

 leaf-bhides.* 



3. The sepals may be normally foliaceous, and represent perfect 

 leaves, as in Githago ; similarly are the two inner sepals of Poh/gala, 

 those of Dipterocarpus, of Ilelleborus niger, and of Ruinex, in the 

 fruiting states. 



In abnormal retrogressive metamorphoses the calyx may become 

 foliaceous. Thus, in Primula the jjoiiits of the sepals develope into 

 broad foliar expansions ; in the rose they become compound leaves, 

 while in monstrous states of Trifoliuin rcpenn the points develope 

 into basal leaf-sheaths, which are prolonged into true petioles 

 bearing ternate leaflets above ; while stipules may actually appear 

 on the borders of the so-called calyx-tube. They thus reveal the 

 true natiu'e of the tube as being receptacular (caulome) and 

 not calycinc (phyllome). 



If the calyx be provided with an epicalyx or calicule, as in the 

 Malcacece and Polentillece, this appears to consist of stipules ; the 

 two between any two leaves or sepals being fused into one organ, 

 though often having the apices of the two sepals fi-ee, thereby 

 revealing their double origin, as figured by Payer. f 



The normal functions of sepals may be classified as follows : — 



1. Protective, as in all buds where a calyx exists. They develope 

 the first of the floral whorls, and are for some time relatively much 

 larger than the remaining parts, which they consequently completely 

 envelope. 



2. Nourishing , as whenever they are green they have ordinary leaf- 

 functions, — (1) when protecting the immature or floral organs. In 

 this state they probably absorb much of the carbon dioxide given off 

 during the respiration of the stamens in their development. (2) In 

 fruiting states, when the calyx is persistent and green, it in many 

 cases gi'ows considerably after the anthesis is over. The basal 

 lobes of the sepals of Viola, the expansions in the sinuses of Cam- 

 panula, and the long lamina to the sejjals of Githago, etc., would 

 increase the green surface for assimilation. (3) They may store up 

 nutritive matter in a fleshy condition, as in JElceagnus, pine-apple, 

 and mulberry. 



3. Attractive. The sepals are often petaloid and coloured, and 



* This difference occui's also in Dlpterocarpus and Musscpncla, and simply 

 means that these sepals represent a more primitive t)-pe of leaf-blade ; for the 

 pinnate venation with a well -developed midrib is a more advanced stage than the 

 palmate. This is well seen in foliage of the pinnately- leaved palms as com- 

 pared with those with fan-shaped or palmate leaves. In transitional states from 

 a single to a double flower of Huxifrarjn dccipiens, described and figured by 

 M. C. Morren in ' Les Bidletins de I'Academie Royale de Belgique,' tome xvii, 

 part 1, p. 415, the newly-formed petals (in the place of stamens), as also 

 the normal petals of the flower, exactly corresponded both in shape and venation 

 with the cotyledons. 



t 'Elements de Botanique,' p. 90, fig. 144. 



