COURSE OF THE BUNDLES IN THE STEM. 287 



there (by a foliar gap), and opposite these points are foliar bundles in the cortex, such as 

 Karsten ' illustrated in the case of Alsophila pruinata. 



Sect. 83. If the structure just described for stems with leaves in several rows be 

 imagined to be transferred to horizontally growing stems with leaves alternating in 

 two rows, there are thus obtained foliar gaps in two alternating rows right and left, 



Fig. 134. — Davallia dissec- 

 ta ; rhizoir.e ; slightly mag- 

 nified. ^ vascular bundle- 

 system, the cylindrical sur- 

 face reduced to a single 

 plane; upper bundle, u 

 lower bundle, b point of in- 

 sertion of a leaf, at X point 

 of origin of a lateral shoot ; 

 B transverse sectiuiL After 

 Mettenius. 



U I) 



n 



Fig. 135. — Aspidium coriaceum ; 

 rhizome ; slightly magnified ; after 

 Mettenius. j4 bundle-system, the 

 cylindrical surface reduced to a 

 single plane ; meaning of the let- 

 ters as in Fig. 134. B transverse 

 section. 



Fig. 136. — Polypodium fraxinifolium ; rhizome ; 

 slightly magnified ; after Mettenius. -A bundle- 

 system, the cylindrical surface reduced to a 

 single plane ; t? upper bundle, o insertion of a leaf, 

 X points of origin of the lateral shoots. B trans- 

 verse section. 



limited by one bundle with a median upper course, and by one median one below, and 

 by alternating transverse bundles between the two. This arrangement is found in 

 many forms as described, or with unimportant modifications^. Comp. Figs. 134, 135. 



* Vegetationsorg. d. Palmen, Taf.' IX. fig. i. 



* Mettenius, Angiopteris, p. 544. Special deviations and irregularities described by Trecul, /. c. 



