Text-book of botany, morphological and physiological . nging to it, and agrees altogether with growth byintussusception. The thin entirely homogeneous lamella of cellulose which bounds the youngcells never allows a separation into two lamellae to be recognised; the bounds of thetwo cells are never marked by a fissure dividing the partition-wall. Nevertheless sucha splitting of the still very thinlamella often takes place laterlocally, when the surface growsmore quickly, as in the forma-tion of the intercellular space ofthe large-celled succulent tissue(parenchyma) of vascular plants,in the for
Text-book of botany, morphological and physiological . nging to it, and agrees altogether with growth byintussusception. The thin entirely homogeneous lamella of cellulose which bounds the youngcells never allows a separation into two lamellae to be recognised; the bounds of thetwo cells are never marked by a fissure dividing the partition-wall. Nevertheless sucha splitting of the still very thinlamella often takes place laterlocally, when the surface growsmore quickly, as in the forma-tion of the intercellular space ofthe large-celled succulent tissue(parenchyma) of vascular plants,in the formation of stomata, & 58 shows some fully grownparenchyma-cells from the stemof Zea Mais in transverse section;the cells were at first boundedby perfectly flat walls, which metnearly at right angles. As thegrowth increased, a tendency towards the rounding off of the polyhedral formsarose; the unequal growth clearly leads to tensions which are compensated by thefact that on the line where one wall meets the other, the cohesion is destroyed in. Fig. 58.—Transverse section through the succulent parenchyma of the stemof Zea Mais; gw common partition-wall of each pair of cells; z intercellularspace caused by their splitting {X5S0). 72 MORPHOLOGY OF TISSUES. the interior of the substance of the cell-wall. Thus a fissure arises which, cor-responding to the relationship pointed out, assumes the form of a triangular prismwith concave sides (Fig. 58, z). It becomes filled with air, and now becomes one ofthose intercellular spaces which very usually form in the parenchyma a continuoussystem of narrow channels. Not unfrequently the portions of the wall which confinethe intercellular space grow rapidly, and thus it increases in width; the cells assumeirregular outlines, or appear star-shaped in transverse section, touching one anotheronly at small portions of the surface (as in the parenchyma on the under side ofmany leaves of Dicotyledons, and the stems oi/uncus cffusus). In the mid
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
