. Botany for high schools and colleges. Botany. 446 BOTANY. lar and interfascicular cambium layers are composed oi elongated cells, which multiply by fission in a tangential di- rection, and thus give rise to radiating rows of cells (Figs. 334 and 335). In a tangential section the cambium cells present an elongated outline, and their extremities are usually more or less oblique (Fig. 336). From these cells there develop various tissues. Thus, on the one side, the phloem iiarencliyma, sieve and fibrous tissues may be pro- duced by more or less gi-eat modifications (Fig. 337). On the other side
. Botany for high schools and colleges. Botany. 446 BOTANY. lar and interfascicular cambium layers are composed oi elongated cells, which multiply by fission in a tangential di- rection, and thus give rise to radiating rows of cells (Figs. 334 and 335). In a tangential section the cambium cells present an elongated outline, and their extremities are usually more or less oblique (Fig. 336). From these cells there develop various tissues. Thus, on the one side, the phloem iiarencliyma, sieve and fibrous tissues may be pro- duced by more or less gi-eat modifications (Fig. 337). On the other side (the xylem side) new ves- sels, fibres, and parenchyma are also devel- oped (Fig. 338). The development of these tissues begins in the inner and outer layers of the cambium, and advances to- ward the central layers. It never hap- pens, however, that all the cambium lay- ers pass over into peiananent tissues, there always remaining one or a few moristem layers. 546.âA study of Figs. 336-338 will show the probable mode of development of the permanent tissues from the meristem tissue of the cambium. It is evident from a comparison of Figs. 326 and 337 that the phloem parenchyma is jiroduced by â the formation of several transverse parti- Fig. row of . J -J. ⢠, cells marked xâx in tions m each camDium cell, and it is prob- Flg. 3*1; r. phloem '.h, ,,,-., . ⢠xi ⢠j ⢠j. xyTem;at« are seen the able that in many cases there IS a direct fisHJons of the cambium - j> i ⢠n ' j. â cells, xeoo. âAfter conversion oi cambium cells mto sieve â "'^^'l'^" tubes. That the cambium cells may be converted directly into tracheides is evident from Fig. 336, and also Fig. 75 (p. 84). In Fig. 338 it is plain that the fibrous tissue {If) and trachGides {f) have the same origin, and the indications are that oven the large pitted vessels {gg) are formed from cambium cells by the great increase in the diameter of the latter, the thickening of their vertical w
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1885
