172 MINUTE STRUCTURE OF THE FLOWER. 



cell-wall, the proper cell-wall of the pollen-grains. This wall 

 may be variously marked, sculptured, and cuticularized, giving 

 rise to the characteristic forms and features of the grains as 

 the}' are met with in the mature flower. In gymnosperms, the 

 development of pollen-grains differs from that described in some 

 particulars which are interesting chiefly from their resemblance 

 to what occurs in the higher cryptogams. 



481. The stigma is a surface formed of peculiar cells which 

 secrete a viscid, saccharine matter, slightly acid in reaction. In 

 some cases the walls of the stigmatic cells undergo the mucilagi- 

 nous modification (Solanum, etc.). The wide differences which 

 exist in the character of the cells of the stigma are illustrated by 

 the following examples: (1) cells with no marked papillae, as in 

 Umbelliferae ; (2) papillose, as in Salvia, Convolvulus, Spiraea ; 

 (3) hairy, as in Hypericum, Geranium ; (4) with compound hairs, 

 as in Reseda. In some of the above the cells are rather loosely 

 aggregated, while in others the}' are much more compactly com- 

 bined. Below the stigma the style often has collecting hairs, as 

 in Compositae, Campanulaeese, etc. (see Volume I. page 222). 



482. The style is a prolongation of the ovary, and shares with 

 it its fascicular system. In the interior there is a slender thread 

 of loose tissue made up of thin-walled cells containing consider- 

 able food-material, starch or oil, etc. The cell-walls often pass 

 into the mucilaginous condition. The st^yle is sometimes tubular, 

 and lined with the tissue just described. 



483. The simple ovary is a modified leaf-blade provided with 

 epidermis, parenchyma, and a fascicular system. The epidermis 

 of the outside of the ovary, and that which lines its cavity, may 

 have all the characters of ordinary epidermis ; stomata and hairs 

 ma}' be present, the latter often being mere papillae, which upon 

 the ripening of the ovary into the fruit become long hairs. 



484. In the interior of the ovary there is frequently a pecul- 

 iar modification, either of the epidermis itself or of the sub- 

 jacent parenchyma as well. In such cases very loose tissue, 

 sometimes appearing as if composed of felted hairs, lines the 

 cavit} T of the ovary (or is found at some one portion of it). The 

 walls of this tissue may undergo the mucilaginous modification 

 either in whole or in part. Its cells contain a considerable 

 amount of food-materials (oil and starch). This loose tissue, 

 together with that of the same character found in the style, is 

 known as conductive tissue, and serves as a path of least resist- 

 ance for the penetrating pollen-tube (see Part II.). 



485. The distribution of the fibro-vascular bundles in ovaries 



