. Botany for agricultural students . Botany. PINES (PINACEAE) 451 maining portion of the nucellus hardens, so that the seed when mature resembles some of the stone fruits, such as the Plum, although it is a seed and not a fruit. It is obvious that a seed is simply a transformed megaspo- rangium. In the Cycads a seed is a megasporangium which has its outer portions modified for protection and contains within a female gametophyte bearing a . young sporophyte. Thus the re- duction of the female gametophyte through the Pteridophytes and finally its retention in the mega- sporangium in the Cycads s
. Botany for agricultural students . Botany. PINES (PINACEAE) 451 maining portion of the nucellus hardens, so that the seed when mature resembles some of the stone fruits, such as the Plum, although it is a seed and not a fruit. It is obvious that a seed is simply a transformed megaspo- rangium. In the Cycads a seed is a megasporangium which has its outer portions modified for protection and contains within a female gametophyte bearing a . young sporophyte. Thus the re- duction of the female gametophyte through the Pteridophytes and finally its retention in the mega- sporangium in the Cycads so that the young sporophyte also develops within the megasporangium were important steps in the evolution of the seed. ' 'Although the Cycads resemble Ferns in having swimming sperms, and in having leaves and stems that are Fern-like, they contrast with them in such new features as differ- entiation of strobili, simpler ga- metophytes, pollination, growth of pollen tubes, and the seed. Pines (Pinaceae) The Pines are a subdivision of the Pine family {Pinaceae). In addition to the Pines, the Pine family in- cludes the Spruces, Firs, Hemlocks, Larches, Cedars, Redwood, Cypress, and others. The Pine family is an exceedingly important one because it includes a large proportion of the trees from which lumber is obtained. The Pine family belongs to the order of Conifers (Coniferales), so named because of the cones which they bear. Not all of them, however, bear dry cones like the Pines, for some have fleshy fruit-like structures, as the berry-like structures of the Junipers illustrate. All of the representatives of the Pine family are interesting, but a study of their life history will be limited to that of the Fig. 400. — Pine sporophjftes. After Miss 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 work
Size: 1104px × 2263px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
