. Botany for high schools and colleges. Botany. 122 BOTANY. of one or more tissues; this reduction may be so great as to leave bat a single tissue, which in many cases is composed of only a few spiral vessels or tracheides (Fig. 109). In other cases, instead of spiral vessels the bundle may consist of a few fibres of bast; or of elongated, thin-walled cells, which are doubtless to be regarded as meristem-cells which failed to fully change into one of the or- dinary joermanent tissues ; this last is a very common accom- paniment of reduced bundles. {a) In the study of the structure of fibro-vas
. Botany for high schools and colleges. Botany. 122 BOTANY. of one or more tissues; this reduction may be so great as to leave bat a single tissue, which in many cases is composed of only a few spiral vessels or tracheides (Fig. 109). In other cases, instead of spiral vessels the bundle may consist of a few fibres of bast; or of elongated, thin-walled cells, which are doubtless to be regarded as meristem-cells which failed to fully change into one of the or- dinary joermanent tissues ; this last is a very common accom- paniment of reduced bundles. {a) In the study of the structure of fibro-vascular bundles much care is required in the preparation of the specimens. The thin transverse sec- tions are obtained by ordinary pro- cesses with no great difficulty, but such is not the case with the lon- gitudinal sections ; they must not only be extremely thin, but must run parallel with the cells and fibres, and moreover, must be sufficiently large to show all, or a considerable part, of the bundle. It is necessary also to have several longitudinal sections, and to know the exact posi- tion of each one when compared with the transverse section. (h) The most satisfactory results can be obtained only by the use of some mechanical section-cutter.* In most cases the sections are made more easily after soaking the stems, roots or leaves used in alcohol. (c) In many cases it is profitable to macerate some of the longitudi- nal sectiouiS in nitric acid and potassi- um chlorate (Schulze's maceration), so as to permit of an isolation of the fibres, cells, and vessels. {d) Good specimens for study may be obtained from any of the higher plants, but the examination will be most profitable if the order * For the various contrivances used for cutting sections see the com- mon books on microscopy, also American Naturalist, 1874, p. 59; American Quarterly Microscopical Journal,1%'^iQ, p. 131, and several articles in Qr. Jour. Mic. Science, 1870, 1874, 1875, Fig. 109.—Terminal rami
Size: 1147px × 2177px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisher, booksubjectbotany
