. Morphology of angiosperms (Morphology of spermatophytes. Part II). Angiosperms; Plant morphology. 108 MORPHOLOGY OF ANGIOSPERMS that often finger-like processes are put out at the side or base of the sac, extending toward the vascular bundles; and in Sty- lidaceae, immediately after the entrance of the pollen-tube, the micropylar part of the embryo-sac grows out into an enormous haustorium much larger than the rest of the sac (Fig. 50). As a result of his investigations of Polypompholyx and Byblis, Lang 91 not only discovered conspicuous haustoria, but used this character, along with others,
. Morphology of angiosperms (Morphology of spermatophytes. Part II). Angiosperms; Plant morphology. 108 MORPHOLOGY OF ANGIOSPERMS that often finger-like processes are put out at the side or base of the sac, extending toward the vascular bundles; and in Sty- lidaceae, immediately after the entrance of the pollen-tube, the micropylar part of the embryo-sac grows out into an enormous haustorium much larger than the rest of the sac (Fig. 50). As a result of his investigations of Polypompholyx and Byblis, Lang 91 not only discovered conspicuous haustoria, but used this character, along with others, such as the nucellus with a single row of axial cells, the tapetum de- rived from the single integument, and the united petals, to remove these genera from the arcbiclilamy- deous Droseraceae to the sympetalous Lentibulariaceae. The whole subject of the mecha- nism for the nutrition of the embryo- sac deserves more detailed attention than it has received. In his study of the fleshy plants, D'Hubert,33 on the basis of the appearance and disap- pearance of starch, concludes that the antipodals nourish the sac before fer- tilization, the synergids nourish the nuclei of the pollen-tube and then the nucleus of the egg at the time of fertilization, and the polar nuclei nourish the fertilized egg and give rise to the endosperm (Fig. 51). Such details may prove true fur the Cactaceae and other fleshy plants.* but the larger field is to be traversed first, which embraces all of the mor- phological structures used in obtaining nutritive supplies fur the structures within the embryo-sac, both before and after fer- tilization. Just what mechanism supplies what structure is a subordinate detail and very difficult to prove, besides being an exceedingly improbable division of labor among structures so * D'Hubert concludes that starch is characteristic of fleshy plants, but there is a. large display of standi in Astilbe (Webb ul) and Galium (Lloyd 105), and doubtless in many other non-fleshy
Size: 1116px × 2238px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorcoulterj, bookcentury1900, bookdecade1900, bookyear1903
