The principles of biology . 79—^thesuccessive nodes answering to the successive points of originof the fronds. Conversely, the stem of a grass, Fig. 91, dis-plays just such relations of parts, as would result from the de-velopment of the type shown in Fig. 79, if instead of the nud-ribs thickening into a solid axis, the matter composing thembecame evenly distributed round the foliar surfaces, at the THE MOEPHOLOGICAL COMPOSITION OF PLANTS, 57 same time that tlie inciirved edges of the foliar surfacesunited. The arrangements of th6 tubular axis and its ap-pendages, thus resulting, are still mor
The principles of biology . 79—^thesuccessive nodes answering to the successive points of originof the fronds. Conversely, the stem of a grass, Fig. 91, dis-plays just such relations of parts, as would result from the de-velopment of the type shown in Fig. 79, if instead of the nud-ribs thickening into a solid axis, the matter composing thembecame evenly distributed round the foliar surfaces, at the THE MOEPHOLOGICAL COMPOSITION OF PLANTS, 57 same time that tlie inciirved edges of the foliar surfacesunited. The arrangements of th6 tubular axis and its ap-pendages, thus resulting, are still more instructive than thoseof the soHd axis. For while, even more clearly than in theDendrohium, we see at the point b, a continuity of structurebetween the substance of the axis below the node, and thesubstance of the sheath above the node; we see that thissheath, instead of having its edges united as in Dendrohium,has them simply overlapping, so as to form an incompletehollow cylinder which may be taken off and unrolled;. and we see that were the overlapping edges of this sheath,united all the way from the node a to the node b, it wouldconstitute a tubular axis, like that which precedes it or likethat which it includes. And then, giving an unexpectedconclusiveness to the argument, it turns out that in -onefemily of grasses, the overlapping edges of the sheaths doimitc : thus furnishing us with a demonstration that tubidarstructures are produced by the incurving and joining oifoliar surfaces; and that so, .hollow axes may be interpretedas above, without making any assumption unwarranted byfact. One farther correspondence between the type thus ideally constructed, and the endogenous type, mustbe noted. If, as already pointed out, the transverse growth of 58 MOEFHOLOGIOAl DEVELOPMENT. an axis arises, when the axis comes to be a channel of circu-lation between all the roots at one of its extremities and allthe leaves at the other; and if this lateral bulging must in-crease, as fas
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectbiology, bookyear1864
