. Foundations of botany. eat groups of plants,such as the lilies, the sedges, and thegrasses, are commonly parallel-veiiied^that is, with the veins running nearlyparallel, lengthwise through the blade,as shown in Fig. 100, orwith parallel veins pro-ceeding from a midrib and thence extend-ing to the margin, as shown in Fig. Occurrence of Netted Veining andof Parallel Veining. — The student hasalready, in his experiments on germina-tion, had an opportunity to observe thedifference in mode of veining betweenthe leaves of some dicotyledonous plantsand those of monocotyledonous
. Foundations of botany. eat groups of plants,such as the lilies, the sedges, and thegrasses, are commonly parallel-veiiied^that is, with the veins running nearlyparallel, lengthwise through the blade,as shown in Fig. 100, orwith parallel veins pro-ceeding from a midrib and thence extend-ing to the margin, as shown in Fig. Occurrence of Netted Veining andof Parallel Veining. — The student hasalready, in his experiments on germina-tion, had an opportunity to observe thedifference in mode of veining betweenthe leaves of some dicotyledonous plantsand those of monocotyledonous difference is general throughoutthese great groups of flowering is the difference? The polycotyledonous pines, spruces, fig. loi. — Parallel , ,, .« . 1 T Veining in ^Jannaiil and other coniferous trees nave leaves veins running fromwith but a single vein, or two or three -i^rib to margin,parallel ones, but in their case the veining could hardlybe other than parallel, since the needle-like leaves are so. LEAVES 137 narrow that no veins of any considerable length couldexist except in a position lengthwise of the leaf. The fact that a certain plan of venation is found mainlyin plants with a particular mode of germination, of stemstructure, and of arrangement of floral parts, is but oneof the frequentcases in botanyin which thestructures ofplants are corre-lated in a waywhich it is noteasy to explain. No one knowswhy plants withtwo cotyledonsshould haven e 11 e d-v e i n e dleaves, but manysuch facts as thisare familiar toevery botanist. 147. Simpleand CompoundLeaves. — Theleaves so far studied are simple leaves^ that is, leaves of whichthe blades are more or less entirely united into one wliile in the elm the margin is cut in only a littleway, in some maples it is deeply cut in toward the basesof the veins. In some leaves the gaps between theadjacent portions extend all the way down to the petiole
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectplants, bookyear1901
