56 STIGMARIA FICOIDES. 



Rootlets. — Secondary organs of Stigmaria performing root-functions, but having 



a different structure from the roots. 

 Rootlet bundle. — A fibro-vascular bundle derived partly from the exogenous or 



centripetal vascular cylinder of the root, and partly from the cambiform or 



phloem zone which immediately invests the exogenous cylinder. 

 Rootlet-bundle Cyltndee. — A cylinder consisting of several layers of cells 



surrounding both the xylem and phloem elements of the bundle in the rootlets 



of Stigmaria. 

 Rootlet-cortex. — The outer wall of each cylindrical rootlet of Stigmaria, an 



extension from the most external or parenchymatous layer of the root-bark. 

 Rootlet-cushion. — A solid cylinder of cellular tissue embedded in the meristemic 



zone of the root-bark, and transmitting the rootlet bundle through its centre. 

 Rootlet-soaks. — Hollow depressions left on the outer surface of a Stigmarian root 



by the disappearance of the rootlets. The latter have been mechanically 



broken off, not being deciduous like a falling leaf. 

 Scleeous tissue oe Sclerenchyma. — Cells or tubes of any kind of which the walls 



are uniformly thickened by woody deposits on their inner surfaces. 

 Teacheids. — Single elongated prosenchymatous cells, the ends of which have not 



been absorbed, which, when living, contained no protoplasm, and whose walls 



also are usually furnished with bordered pits. 

 Vegetative Repetition. — Multiplications of any organ, each of which multiplied 



examples has typically the same structure and functions as those which it 



resembles. 

 Vessels. — Prolonged tubes, usually formed by the coalescence of linear series of 



cells, the divisions (septa) between the ends in mutual contact having been 



partially or entirely absorbed. 



