. Essentials of botany. Botany; Botany. HISTORY OF THE PLAXT KINGDOM 301 generation being smaller and wholly dependent for its food supply on the other generation to which it is attached. 382. Development of the Plant from the Spore in Pteridophytes. â In the f pteridophytes there is an alternation of generations, but here the proportions are reversed, the prothallium, or sexual generation, or gametophyte, being usu- ally short-lived and small (sometimes microscopic), and the non-sexual gen- eration, the sporophyte, often being of large size. The ferns (non-sexual generation), for instance, ar
. Essentials of botany. Botany; Botany. HISTORY OF THE PLAXT KINGDOM 301 generation being smaller and wholly dependent for its food supply on the other generation to which it is attached. 382. Development of the Plant from the Spore in Pteridophytes. â In the f pteridophytes there is an alternation of generations, but here the proportions are reversed, the prothallium, or sexual generation, or gametophyte, being usu- ally short-lived and small (sometimes microscopic), and the non-sexual gen- eration, the sporophyte, often being of large size. The ferns (non-sexual generation), for instance, are peren- nial plants, some of them tree-like. Some pteridophytes, as the Salvinia, a small, floating aquatic plant sometimes known as a water-fern (Fig. 216), pro- duce two kinds of spores, the large ones known as megaspores, and the small ones as microspores (Fig. 217). Both /, floating leaves; r, sub- kinds produce '"^'^sf '''^^'^^' f 1"^ â¢â ^ _ as roots; s, spore-fruits. microscopic prothallia, those of the former bear- ing only archegonia, those of the latter only antheridia. From the prothallia of the megaspores a plant Fig. 217. Two Indusia of (non-sexual generation) of consid- erable complexity of structure is formed. 383. Parts of the Flower which correspond to Spores. â In seed-plants the spore-formation of spore-plants is represented, though in a way not at all. 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 Bergen, Joseph Y. (Joseph Young), 1851-1917. Boston, Ginn
Size: 1038px × 2408px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1908
