COURSE OF THE BUNDLES IN THE STEM. 



291 



The investigation oi a. young stem of Angiopteris showed me a completely typical bundle- 

 tube, interrupted by wide foliar gaps ; two strong foliar bundles arise below at the lateral 

 margins of the gap, and ascend obliquely through the cortex, within which they divide 

 into the branches which pass out into the leaf. 



The concentric zones of thin bundles in the stem of Ceratopteris thalictroides may 

 also belong to this category, but require further investigation. Comp. Mettenius, /. c. 

 p. 530. ■ ... 



c. Accessory medullary and cortical bundles in addition to the simple tube of bundles. 



Sect. 85. Among the Cyatheacea, according to Mettenius, the above-mentioned 

 forms (p. 286) have only the typical tube, perforated by foliar gaps, and consisting 

 of flattened vascular bundles, the margins of which next the gaps are curved out- 

 wards. Other species, including the majority in the genera Cyathea and Alsophila, 

 have, in addition to the vascular bundles thus disposed, small bundles, which originate 

 from the foliar gaps and traverse pith and cortex, there forming a delicate open 

 network. The relatively thin bundles from the margin of the foliar gap, which pass 

 into the petiole, arrange themselves so that in a transverse section of its insertion, 

 or in the leaf-scar, they are arranged in a curve, convex downwards, and simple, or 

 with the ends turned inwards above : it consists of few bundles in small leaves, e. g. 

 in young specimens of Hemitelia capensis 13-14 bundles, of Alsophila radens Klf. 4, 

 Cyathea arborea Sm. 13'; on the other hand, in strong specimens or species they 

 form two curves with the ends curved inwards, 

 and consisting of many bundles, one of these 

 curves being convex downwards, corresponding 

 to the lower edge of the foliar gap and spring- 

 ing from it, the other convex upwards, and 

 corresponding to the upper margin. The in- 

 curved ends of both curves are directed down- 

 wards and towards the middle of the leaf-scar 

 so that their bundles form on each side two 

 nearly parallel series running to the middle of 

 the scar ^. Compare Fig. 1 38. 



Further, in the space surrounded by the single curve or by the upper one, a 

 relatively small number of bundles pass out into the petiole — e. g. as described by 

 Mettenius in Hemitelia capensis, Alsophila radens, and Cyathea arborea two each, in 

 a species of Cyathea 7, in Alsophila Haenkei 4, in Cyathea Imrayana 2 or 4, in C. 

 ebenina 2. These do not arise from the margin of the foliar gap, but are connected 

 both inside and outside it with the margin itself, as well as one with another, by 

 numerous strong anastomoses (usually sheathed with sclerenchyma) : they then run 

 through the foliar gap downwards into the pith. (Figs. 139, 140, m) 



Immediately after their entry they pass with a steep curve inwards and down- 

 wards, and divide into branches diverging acutely downwards; these sometimes 



Fig. 138. — Cyathea Imrayana; natural size. Two 

 old leaf-scars from a dead stem ; a lower, b higher on 

 the stem; a with four, b with two medullary bundles 

 above yn. 



^ Mettenius, Angiopteris, /. c. Taf. V. , 



2 Mohl.in Martius, Icones,/.^., Verm. Schriften, p. no.— Numerous valuable details in Trecul. 

 l.c, XII. p. 270. 



U 2 



