摘要:

Summary.1The investigation was started in the hopes of throwing some light upon the problem of sap supply to the upper parts of leaves which grow by a basal meristem, but has been extended as a developmental study of the shoot.1The scattered bundles of the stem may be classified into four groups–(a) medullary, (b) perimedullary, (c) cortical, (d) peripheral. At the nodes the bundles of the different series are in connection.1up the second internode as the perimedullary bundles which constitute the leaf‐trace. The differentiation of the protoxylem of the primary longitudinal veins of the leaf takes place basifugally, but when this differentiation reaches the leaf‐apex, the direction of sap‐flow is reversed, with the result that the secondary longitudinal and transverse veins develop basipetally in the leaf, and lead to the basipetal development of the cortical and peripheral stem‐bundles.1The internode grows by an intercalary basal meristem–the disappearance of which may be traced in a basipetal direction by the gradation in cell size and the micro‐chemical reactions of the cell‐walls in an elongating internode. The peripheral bundles develop in the region of the peripheral meristem, and in the course of development become surrounded by an endodermis, which is later converted into a sclerenchymatous bundle‐sheath, continuous with the sclorenchyma sheath running round the stem.1The leaf primordium consists of an incomplete ring of tissue which later differentiates into sheath and lamna. The differentiation of the leaftissues follows the same general plan as the vascular development, taking place chiefly in a basipetal direction.The effect of etiolation is to produce relatively narrower leaves.1The following points are discussed as being of importance in the development of the shoot inTradescantia, and as probably bearing upon the Monocotyledon in general:–(a). The absence of secondary meristems and consequent importance of the portions of the primary meristem, isolated as intcrcalary stem and leaf meristems.(a). The zonal upgrowth of a few leaves from intercalary rings of meristom.(b). The reversal in the direction of sap‐flow from the apex of the lamina with its effect upon the irrigation of the basal meristem of leaf and internode, the formation of leaf auricles, and finally in the development of the peripheral stem‐bundles as alternative channels of vascular supply to younger parts of the shoot when the older channels are ruptured by clongation of the internode.(c). The zonal distribution of meristem accounts for the continued growth of partly developed leaves under etiolation conditions. No new leaf initials separate from the apex during growth in darkness.7It is shown that the change in shape of the leaves ofAlisma, when grown in darkness, might be anticipated from a considoration of the developmental conditions under whic

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1925.tb00500.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1925.tb00501.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

摘要:

Summary.1The seedlings of the seventeen species ofLupinusexamined are uniformly diarch in plan.2They may, from an anatomical standpoint, be arranged in a series, withL. nanusat one end andL. albusat the other.3Commencing withL. nanusthis series shows a progressively wider separation of the two metaxylem groups from the central protoxylem and a lowering of the level at which typical root‐structure is attained.4It is considered that the initial stages in the separation of the xylem groups are brought about by the replacement of the tangentially developed elements termed by Chauveaud “vaisseaux intermédiaires” by parenchyma. This process is carried further, owing to a phylogenetic shifting outwards of the metaxylem groups.5It is considered that the final term in this series may represent one of the steps by which diagonal tetrarchy has been attained.6The evidence yielded by aberrant specimens of some species and commonly occurring variants of others is held to support Compton's view of the primitiveness of tetrarchy within the Leguminosæ.The authors desire to record their thanks to the Regius Keeper of the Royal Botanic Gardens, Edinburgh, the Director of the Royal Gardens, Kew, the Director of the Botanic Gardens, Cambridge, and the Director of the Imperial Institute, London, for gifts of seeds, without which this work would not have been p

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1925.tb00502.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1925.tb00503.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1925.tb00504.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1925.tb00500a.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY