. Botany of the living plant. Botany. 240 BOTANY OF THE LIVING PLANT to contain Jour loculi, or pollen-sacs, two being placed on eitlier side of a central connective, which is simply a continuation upwards of the filament. A single vascular strand which traverses the filament IS continued upwards into the anther, where it fades out usually without any branching (Fig. 192, A). However unlike a foliage leaf the stamen so constructed may appear to be, there is no reasonable doubt of its foliar nature. It arises from the axis like a leaf, and in acropetal succession, while in " doubled "
. Botany of the living plant. Botany. 240 BOTANY OF THE LIVING PLANT to contain Jour loculi, or pollen-sacs, two being placed on eitlier side of a central connective, which is simply a continuation upwards of the filament. A single vascular strand which traverses the filament IS continued upwards into the anther, where it fades out usually without any branching (Fig. 192, A). However unlike a foliage leaf the stamen so constructed may appear to be, there is no reasonable doubt of its foliar nature. It arises from the axis like a leaf, and in acropetal succession, while in " doubled " flowers it may not un- frequently be seen to be transformed into a petal, or even into a green. Fig. 193. Lobe of anther ol Ca/i/ia cut transversely, showinj,^ two pollen-sai?s at maturity, wittt the fibrous layer immediately below the epidermis. For details see text. ( .'. 100.) F. O. B. leaf of the foliage type. But better evidence is obtained by comparison of earlier fossil Seed-Plants, in which the organs bearing pollen-sacs are actually leaf-like. It may then be accepted that the stamens are leaves, specialised for bearing pollen-sacs or micro-sporangia. Each pollen-sac is enclosed til! it is ripe by a wall consisting of several layers of cells. In most stamens the slit of dehiscence runs longitudinally, following the line where the walls of the two sacs of one anther-lobe join with the septum that separates them (Fig. 193). There the cell-walls arc thin, and the cells themselves arc rounded off by intercellular spaces, so that they easily come apart. The slit thus formed gapes widely, owing to the action of the walls of the pollen-SLics. Below their superficial epidermis lies a layer of fibrous cells, the inner cell-walls of wliich are thicker than the outer, while fibrous bars running outwards along their lateral walls prevent radial collapse. The eft'cct on these cells of. Please note that these images are extracted from scanned page images that may have been digitally
Size: 1743px × 1434px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
