386 



PRIMARY ARRANGEMENT OF TISSUES. 



of the investigated species of Aspidium have according to Stenzel's account three or five 

 bundles for each leaf, one median, one from the lower angle, the others arising in pairs 

 from the sides of the mesh : in Aspidium Thelypteris the median one is absent, according to 

 Stenzel (Tab. V. i8), one bundle passing into the leaf from each side at the middle of the 

 very elongated mesh. Blechnum Spicant (Stenzel, Tab. II. 5) has two lateral ones, one 

 arising on each side, close to the lower angle of the mesh, Bl. brasiliense however has seven, 

 one median and three pairs of lateral ones, arising from the lower half of the mesh. In 

 Asplenium Filix fcemina, the mature rhizome of Struthiopteris ^ in Aneimia, and Ophio- 

 glossum the same arrangement is found, which appears only in the young plant of Filix mas, 

 viz. each leaf receives only one median bundle from the lower angle of its gap. It is 

 remarkable, according to Stenzel's account {I.e. Tab. II. 3), that in the scale leaves of the 

 elongated runners of Struthiopteris the median bundle is absent, and in its place a bundle 

 runs on each side from the middle of the long mesh. 



Among the Cyatheacese, Dicksonia (Balantium) antarctica, Karsteniana, Cibotium 

 Schiedei, glaucescens, Plagiogyria biserrata, Alsophilia pruinata, blechnoides^ have— in 

 contradistinction to their nearest allies to be described below— the same structure as is 

 now under discussion. The appearance of the transverse section of most of these plants, 

 which differs so strikingly from that of the Polypodiacese, depends partly upon the form 



Fig. 132,— Aspidium Hilix inas ; natural size, ^slightly magnified ; D end of the stem, 



. the leaves of which are cut off, excepting the highest ones ; * transverse section of a 



petiole ; -w roots ; B a similar end of a stem, the network of bundles exposed by paring 



off the cortex (^) ; ^ mesh of the net, with insertions of the foliar bundles ; C base of the 



petiole, with a lateral bud ft, longitudinal section ; 7V root. From Sachs' Textbook. 



FIG. 133. — Aspidium Filix mas ; 

 transverse section through a strong 

 stem, with 8/zi leaf-arrangement; 

 natural size. 



of the vascular bundles in the stem itself, these being broad plates, usually curved out- 

 wards at the margin, with narrow foliar gaps ; partly upon the massive dark brown bands 

 of sclerenchyma surrounding these bundles; partly upon the large number of thin 

 foliar bundles, or the presence of one or a few broad channel-shaped ones ; finally upon 

 the very oblique ascent of the foliar bundles through the cortex, and the frequent anasto- 

 moses in this part of their course between those belonging to one leaf (comp. Fig. 141, 

 p. 293). If the internodes are short the transverse section shows a circle surrounding 

 the pith, composed of bundles elongated in the direction of the periphery, or curved out- 

 wards in a horseshoe-like manner, and with brown sheaths : between these are medullary 

 rays of unequal breadth, according as the section has passed through foliar gaps at vary- 

 ing height ; outside the ring of bundles are those bundles which are passing to the leaves ; 

 where the internodes are elongated and the foliar gaps are of relatively small size, the 

 transverse section may show one closed annular bundle, which is only broken here and 



' Hofmeister, l.i. 



Mettenius, Angiopteris, p. 524. 



