. The classification of flowering plants. Gycas, a stoutcolumnar trunk is formed which with its crown of huge pinnateleaves recalls the habit of a tree-fern or date-palm (fig. 4, A). The leaves form a terminal crown and are spirally are of two kinds; brown, often roughly felted scale-leavesand large compound foliage-leaves, a series of each being pro-duced in turn, the former in larger numbers preceding andcovering the latter in the bud. A year or longer intervenesbetween the appearance of each group of foliage-leaves. Thestout, sometimes thorny, petiole springs from a small thic
. The classification of flowering plants. Gycas, a stoutcolumnar trunk is formed which with its crown of huge pinnateleaves recalls the habit of a tree-fern or date-palm (fig. 4, A). The leaves form a terminal crown and are spirally are of two kinds; brown, often roughly felted scale-leavesand large compound foliage-leaves, a series of each being pro-duced in turn, the former in larger numbers preceding andcovering the latter in the bud. A year or longer intervenesbetween the appearance of each group of foliage-leaves. Thestout, sometimes thorny, petiole springs from a small thickened Ill] CYCADEAE 49 sheath and passes above into a strong rachis on which areborne right and left the sessile, leathery, generally numerouspinnae. The Australian genus Bowenia has bipinnate has a pair of tooth-like stipules. The leaves vary much in size and number, from half a foot(Zamia pygmaea) to 9 or 10 feet, and from only a few inBowenia and Stangeria to more than one hundred in strongplants of Cycas Fig. 4. A. Cycas circinalis. Female plant. (After Blume.) B. Female sporophyll of Cycas pectinata. C. Albumen of C. circinalis cut lengthwise shewing embryo {e) and spiral suspensors removed from central cavity. (After Blume.) D. Male spoi-ophyll of C. circinalis shewing groups of pollen-sacs on under surface. E. Portion of D enlarged shewing four sori. F. Pollen-grain of C. revoluta; p, prothallial or vegetative cell; g, generative cell; f, tube-cell. (After Ikeno.) G. Germinated pollen-grain of Zamia integrifolia ; g, remains of grain; r, vege- tative cell; s, stalk-cell; h, body-cell shewing a blepharoplast at each poleof the nucleus; t, tube-nucleus. (After Webber.)H. Ciliated male-cell of Cycas revoluta. (After Ikeno.) In some genera (Zamia, Stangeria, &c.) the foliage-leavesand the scale-leaves perish entirely so that the older parts ofthe stem are bare. In Cycas and others the leaf-bases and R. 4 50 FLOWERING PLANTS [CH. scales persist a
Size: 1847px × 1352px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1904
