336 



MESSES. CIEIL WEST 



ON 



estio-ations have convinced us tliat the view held by many botanists, who regard the 



primary vascular 



leaf -traces, is untenable 



cylinder of the adult stem as bein 



2" made 



up of a sympodium of 



Por the 



g 



detail below (p. 338) 



adopted the view already 



held by Bruchmann (7), Hegelmaier (15), and Scott and Hill (28), that part, at least, of 



the stele of the adult plant is caulin 



Text-fig. 2. 



u 



•mer 



Diagram showing arrangement of primary and secondary stelar tiasues of Isoetes lacustris. From a 



median longitudinal section of the caudex cut in the plane of the furrows, x 50. 



(For lettering, see text-fig. 1, p. 335.) 



we 



The stele of Isoeles is generally regarded as a single structure (i. e. a stem-stele), but 



two distinct 



confined and 



of the opinion that the stele of the adult sporophyte consists of 



are 



parts, namely, a vertical cylindrical portion to which the leaf-traces 



which constitutes the stele of the stem proper, and a relatively flattened hi- or tri-lobed 



attached (text-figs. 1, 2) 



The latter 



basal portion to which all the root-traces are 



jpropose to call the rhizophore-stele, since it belongs to a perfectly distinct root-bearin 



