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 

 they 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, slightl}* 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 papilla?, as in 

 Urabelliferae ; (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 they are much more compactly com- 

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

 in Composite, Carapanulaceae, 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 style is sometimes tubular, 

 and lined with the tissue just described. 



483. The simple ovar}' 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 

 cavity of the ovary (or is found at some one portion of it). The 

 walls of this tissue ma}* 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.). 



48o. The distribution of the fibro-vascular bundles in ovaries 



