GLOSSARY OF BOTANICAL TEEMS EMPLOYED IN THE 

 MONOGRAPH. 1 



Acropetal. — Where a growing shoot develops other lateral structures or organs 

 in succession, behind the growing tip of the shoot. 



Barred Tissues. — Consist of tracheids or vessels, the walls of which are thickened 

 internally by transverse bars of woody material (lignine) which alternate with 

 parallel thin spaces ; modified scalariform vessels. 



Cambiform Tissue. — Cellular tissue of the phloem produced from the cambium, 

 and which has assumed a permanent condition ; phloem tissues the elements 

 of which are similar in character to that of the cambium in their elongated 

 form and thinness of walls. See De Bary, ' Phanerogams and Ferns,' Eng. 

 Trans., p. 327. 



Cambium. — A thin zone of meristematic cells intermediate between the exterior of 

 the exogenous vascular zone and the innermost surface of the bark, and 

 capable of developing new structures from either or both of its surfaces. It 

 also appears between the xylem and the phloem elements of isolated vascular 

 bundles, e. g. foliar or rootlet bundles. 



Cauline. — Leaf-bearing axes. 



Centrifugal or Exogenous Vascular Cylinder. — A zone of vessels or tracheids 

 surrounding the centripetal cylinder where the latter is present, and increas- 

 ing in thickness by additions made to its outer border through the action of 

 a circle of meristem cells known as cambium ; its growth in thickness there- 

 fore proceeds from within outwards. 



Centripetal Vascular Cylinder. — A zone common to many Carboniferous Crypto- 

 gams, which, commencing as a medullary sheath, increases in size and 

 thickness by a conversion of the medullary cells which it surrounds into 

 vessels or tracheids. Its component elements are never arranged in radiating 

 lines or lamince, and it is the source whence the fibro-vascular bundles going 

 to the leaves are derived. Its growth, therefore, is centripetal, 

 i Iutroduced at the recommendation of the Editor for the use of geologists who may not be familiar 



with botanical terms. 



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