. Botany of the living plant. Botany. MUSCI AND HEPAtlCAE 357 rise above ground, also forming new buds (Fig. 297). In this way the usual gregarious habit is established. In the smaller Mosses the structure of the leafy Plant is very simple. The leaves may consist only of a single layer of green cells (Fig. 72, p. 100), with a strand of elongated cells forming a central vein, which stops at their bases : the stem is here traversed by an independent conducting cord [Mmitm). But in Polylrichum, and other large jMosses, there is a conducting system consisting of a central column of water-conductin
. Botany of the living plant. Botany. MUSCI AND HEPAtlCAE 357 rise above ground, also forming new buds (Fig. 297). In this way the usual gregarious habit is established. In the smaller Mosses the structure of the leafy Plant is very simple. The leaves may consist only of a single layer of green cells (Fig. 72, p. 100), with a strand of elongated cells forming a central vein, which stops at their bases : the stem is here traversed by an independent conducting cord [Mmitm). But in Polylrichum, and other large jMosses, there is a conducting system consisting of a central column of water-conducting tissue, upon which strands from the leaves are. Fig. 299. Transverse section of the central tissues of an aeriai leafy stcni of Polylyuhiiu! commitne, sfiomng entry of leaf-traces into the mantles of the central cylinder. The leaf traces are numbered from without inwards, a";)/= starchy parenchyma, //yrf''= hydroni. /t-/)/= leptom. /o''/. s/'. =hydi-om-shcath. rifrf. ^trj. = rudimentar\- pericvcle. -oo. (After Tansley and Chick.) applied. Each of these consists of hydrom (xylem) and leptom (phloem) (Fig. 299). Thus in the gametophyte of the larger IMosses a structure is seen which offers an analogy with that of the sporophyte of Vascular Plants. A curious structure is seen 111 the leaves of PoJytnchum, and some other Jlosses, which is probably effective in collecting and retaining \vater during rain. The flat blade bears on its upper face numerous longitudinal plates of chlorophyll-parenchyma, sometimes overlapped by the membranous margins of the leaf. In P. commune (Fig. 300) the distal cells of each plate are enlarged, so that its chlorophvll-cells abut upon an almost closed space. As the leaf flattens when moist, and curls its margins upwards when dry, the access of atmospheric air to the parenchyma is controlled as it is by the automatic stomata in Vascular Plants. But this is only an analogy, for the surface.^. Please note that these images are extracted from scanne
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
