. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. 2lH PKIMAfi)' ARRANGEMENT OF TISSUES. in llie same direclion as the root. Their membranes are usually colourless, thus the surface of the air-containing layer appears white and shining. In water, which it quickly absorbs, the layer becomes transparent; the internal green cortical parenchyma then becomes apparent. Another cause of the green colour is that in old roots (Vanda furva and Anselia africana, according to Leitgeb) small green algal cells sometimes enter the cavity of the tra
. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. 2lH PKIMAfi)' ARRANGEMENT OF TISSUES. in llie same direclion as the root. Their membranes are usually colourless, thus the surface of the air-containing layer appears white and shining. In water, which it quickly absorbs, the layer becomes transparent; the internal green cortical parenchyma then becomes apparent. Another cause of the green colour is that in old roots (Vanda furva and Anselia africana, according to Leitgeb) small green algal cells sometimes enter the cavity of the tracheides. When old, the air-containing layer is in many species entirely thrown off (Angraecum subulatum, Cymbidium ensi- folium, Zygopetalum Mackai, according to Leitgeb ; also Vanda furva), or only the innermost layer remains : the result of this also is that the green colour of the cortical parenchyma becomes visible. In Eria stellata the colour of the aerial roots is brown, since the membranes of the tracheides assume a brown colour: in Trichotosia ferox the tracheides of the. FIG. 91.—Median longitudinal n through the apex of a young root of the with the same lettering (375). ; Oncidium as Fig. 90, four-layered sheath are filled with a reddish-brown mass, which gives the roots a reddish-brown colour; the same sometimes applies to .Cymbidium marginatum. Larger or smaller masses of a loosely coherent black-brown substance were found by Leitgeb in many cases, especially in the inmost layer of cells : and in specially large quantity in Renanthera coccinea. According to Leitgeb, those walls which cover the >> short thin-walled endodermal cells always show a limited brown coloration. With the exception of these last-named cases, air alone, or water obtained from without, is always contained in the tracheides; the protoplasm and nucleus dis- appear entirely during their development, close to the growing-point. During their differentiation the walls of the tracheides, like
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Keywords: ., bookcentury1800, bookdecad, booksubjectplantanatomy, bookyear1884
