. Text-book of botany, morphological and physiological. Botany. S°4 PHANEROGAMS, persistence, becoming lignified and often very hard. The numerous pollen-sacs on the under side of the stamens are usually collected into small groups numbering from two to five, like the sori of Ferns, these again forming larger groups on the right and left side of the leaf. The pollen-sacs are globular or ellipsoidal, usually about i mm. in size, and are attached with a narrow base to the under side of the stamen; Karsten states that in Zamia spiralis they are even stalked. They dehisce longitudinally, and are i
. Text-book of botany, morphological and physiological. Botany. S°4 PHANEROGAMS, persistence, becoming lignified and often very hard. The numerous pollen-sacs on the under side of the stamens are usually collected into small groups numbering from two to five, like the sori of Ferns, these again forming larger groups on the right and left side of the leaf. The pollen-sacs are globular or ellipsoidal, usually about i mm. in size, and are attached with a narrow base to the under side of the stamen; Karsten states that in Zamia spiralis they are even stalked. They dehisce longitudinally, and are in all respects much more like the sporangia. FIG. 343.— A carpel of Cycas revoluta (reduced about k)\f pinnae of the leaf-like carpel; sk ovules replacing the lower pinnae; sk' an ovule further developed. of Ferns than the pollen-sacs of other Phanerogams, from which they also differ in the firmness and hardness of their wall. The mode of development of the pollen-sacs and pollen-grains of Cycadeae was till lately unknown; it has only quite recently been observed by Juranyi in Ceratozamia longifolia. The pollen- sacs are formed on the under side of the stamens in the form of small papillae, probably consisting from the first of several cells over which the epidermis of the surface of the leaf is continuous. The inner tissue is next differentiated. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Sachs, Julius, 1832-1897; Vines, Sydney Howard, 1849-1934. ed. and tr. Oxford, Clarendon press
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1882
