216 HOFMEISTER, ON 



gether to form a single one. The transverse section of 

 this single bundle has the shape of a horse-shoe, of which 

 the opening is originally turned towards the apex of the 

 stem-bud, but which in consequence of the rapid longi- 

 tudinal development of the latter, and of the curving up- 

 wards of the frond, appears at a later period to be parallel 

 to the longitudinal axis of the stem. After the splitting 

 of the primary vascular bundle, and the appearance of 

 cortical vascular bundles in the stem, there arise ramifica- 

 tions of both the axile bundles, of the wide bundle above 

 them, and of the rest of the cortical vascular bundles of the 

 adjacent longitudinal half of the stem (PI. XXX, figs. 

 1" to V, and fig. 2). The sheath of vascular bundles also 

 sends out prolongations into the stipes : from the upper 

 as well as from the lower group of brown bast-cells the 

 same transformation of the tissue advances in a direction 

 parallel to the longitudinal axis of the frond (PI. XXX, 

 fig. 7). At a short distance above the place of insertion 

 of the frond, both longitudinal strings of ligneous tissue 

 unite to form a single one of which a transverse section 

 exhibits the shape of the letter T having the two branches 

 of its head turned to the lateral longitudinal ridges of the 

 frond (PL XXX, figs. 8, 9). The hind angle of the T 

 includes the ramifications of the two axile primary bundles 

 of the stem ; the fore angles those of the wide cortical 

 vascular bundle which runs off in the top line of the hori- 

 zontal stem, as well as the branches of the cylindrical cortical 

 vascular bundle immediately adjoining. In front and 

 on the outside of the head of the T, run the bundles which 

 sent forth the cortical bundles underneath the place of inser- 

 tion of the frond. In the lowest part of the stipes, under- 

 neath the point of junction of the prolongations of the 

 vascular sheath, all these vascular bundles anastomose in 

 a radial direction ; above this point only in a tangential 

 direction. Each of the primary vascular bundles sends 

 two proportionally thin cylindrical branches into the frond 

 (PI. XXX, figs. 2 d,e ). All four soon unite to form a wide 

 vascular bundle concave behind (PL XXX, figs. 8, 9). 

 A similar bundle is formed by the junction of those bundles 

 which are enclosed by the fore angle of the T-shaped mass 



