Nature and development of plants . Fig. 248. Development of the sporophyte or embryo of Cycas: A, sec-tion of archegonium, showing a large number of cells lining the walls ofthe germinating gametospore. This is the pro-embryo stage. B, laterstage in which the pro-embryo has developed a suspensor, s, which pushesthe embryo-forming cells, c, into the nourishing tissues of the , still later development, showing the greatly coiled suspensor and theyoung sporophyte or embryo, e, with two cotyledons. D, section of a seedof Zamia: i, integument which is fleshy without and stone-like with
Nature and development of plants . Fig. 248. Development of the sporophyte or embryo of Cycas: A, sec-tion of archegonium, showing a large number of cells lining the walls ofthe germinating gametospore. This is the pro-embryo stage. B, laterstage in which the pro-embryo has developed a suspensor, s, which pushesthe embryo-forming cells, c, into the nourishing tissues of the , still later development, showing the greatly coiled suspensor and theyoung sporophyte or embryo, e, with two cotyledons. D, section of a seedof Zamia: i, integument which is fleshy without and stone-like within;m, micropyle; g, gametophyte; c, dormant sporophyte or embryo.—A-C.—After Treub. which has increased in size until it has absorbed all the tissuesof the sporangium, we call the seed (Fig. 248, D). At thisstage of development, the seed falls from the strobilus and mayremain in a dormant condition for years. The formation of the seed is the most characteristic featureof the Spermatophyta and the most important advance that is
Size: 1548px × 1614px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisher, booksubjectplants
