340 



MORPHOLOGY. 



198 



The perianth of the female flower of 

 Carex is peculiar ; it is originally three- 

 leaved, but one leaf very soon ceases 

 to grow, whilst the others, developing 

 disproportionately, unite by their edges 

 and enclose the stunted leaf, and thus 

 form the tubular envelope of the ger- 

 men, which has been termed utriculus, 

 cupula, &c. (See Plate in., figs, 24. 26., 

 with the explanation.) The perianth 

 of the Grasses is similar (fig. 198.) ; 

 it originally consists of three leaves, of 

 which one (palea exterior) is excessively 

 developed, and encloses the other two, 

 which soon cohere and grow imperfectly 

 into a membranous structure (palea 

 superior binervis. (Plate III., fig. 21 

 23., and explanation.) 



The structure of perianthial leaves is, on the whole, that of very 

 simple leaves, which exhibit no special peculiarities, particularly if 

 they are green. The ramifications of the vascular bundles are 

 therefore simple, the separation into an upper and under paren- 

 chyma layer is seldom exhibited ; but the epidermis usually. In 

 the coloured and delicate parts the cells of the parenchyma contain 

 colouring matter. In general the parenchyma is very loose and 

 almost spongy, with homogeneous, transparent fluid contents, and 

 large intercellular cavities filled with air ; hence the white colour. 

 The epidermis is less developed in coloured leaves, and more 

 resembles the structure of epithelium ; stomata are sometimes pre- 

 sent, especially upon the under surface, but the epidermal cells of 

 the upper surface are often raised in shorter or longer papillae, which 

 give the upper surface the peculiar velvet-like appearance. It is 

 very frequent here to find the secreted layer of the epidermis 

 (cuticle) regularly and delicately striated (aciculatus), which cer- 

 tainly contributes to heighten the brilliancy of the colour, and 

 perhaps, by its effect upon the rays of light, to the production and 

 modification of the peculiar tints. 



Occasionally, especially at the base of hollow forms, no epidermis 

 is produced at certain points, and the parenchyma assumes a pecu- 

 liar structure, to perform the function of secretion of a juice con- 

 taining much sugar ; as, for instance, the nectary at the base of the 

 perianthial leaves of Fritillaria, very various parts on the labellum 

 of the Orchidacece, &c. In rare cases the texture is hard and almost 



198 Phalaris cceruhscens . A, Spikelet : a and b, spathe, formed of two bracteae (valvce 

 glumce, Auct. ) ; c and d, one free and two coherent perianthial leaves (palece, Auct. ) ; 

 e e e, three stamens ; /; a stigma. B, The two coherent perianthial leaves, with two 

 nerves (palea superior, Auct. ). C, Pistil, surrounded at the base by two weakly coherent 

 accessory petals : h A, (squamulce, Auct. ) ; g, germen ; /, one stigma ; the other is cut of 



