COURSE OF THE BUNDLES IN THE STEM. 385 



from one to very high figures. Where several bundles pass out, they often anastomose 

 with one another in a reticulate manner immediately after leaving the fohar gap : 

 this is especially the case in the Cyatheaces. From the various combinations of 

 these different relations result the most various individual forms of the net, and of the 

 grouping of the bundles in the transverse section of the stem : a cylindrical pith is 

 always surrounded by them. 



To this type belong numerous Polypodiacese, a number of the Cyatheaceae, of 

 the Schizseacese, Aneimia, of Ophioglossacese, Ophioglossum (O. vulgatum, O. pe- 

 dunculosum). Peculiarities may be subsequently described in a few examples. 



The seedling of Aspidium Filix mas begins with leaves arranged with J divergence : their 

 solitary bundles are united sympodially in the stem to one axile bundle. Above the 

 5th-6th leaf the stem increases greatly in thickness, the a arrangement passes over to j, 

 and from the point of outward curvature of the bundle of the highest leaf of the a 

 arrangement the formation of the reticulate bundle-tube begins. Each leaf receives 

 one bundle from the lower angle of the rhombic mesh or foliar gap, upon which its base 

 is seated : or, in other words, two bundles run into each leaf, arising from the point of 

 exit of those which pass into the two next lateral older leaves : these converge acutely 

 towards their own point of exit, and are there united into a single bundle. By the repe- 

 tition of this formation the network of rhombic meshes is built up. Where the arrange- 

 ment is J there pass up to leaf 9 one bundle from 6 and one from 7, to leaf 7 one from 

 4 and one from 5, &c. In the second year the plant becomes much stronger, the leaf 

 arrangement passes over to -f^, which divergence is retained in the mature plant, or 

 passes over into ^j;^. 



Each leaf now receives several bundles from the margin of its foliar gap, at first five, in 

 mature and strong stocks seven : one arising from the lower angle, and six from the sides 

 of the mesh ; of the latter two weaker ones on each side, belonging to the lower half of the 

 mesh, and one stronger one belonging to the upper half. The structure of the meshes 

 is the same with fV arrangement as with f ; at the lower angle of each, where the 

 median bundle passes into the leaf, two bundles which descend from the centre of the 

 two next lateral older leaves come into contact — that from the one side following the 

 parastichies composed of every third leaf, that from the other the parastichies composed 

 of every fifth leaf (comp. Fig. 132). The transverse section of the mature stem thus cuts 

 eight vascular bundles (where the arrangement is /y, 10-12 bundles), which form a circle 

 round a wide pith : outside this in the cortex are seen the bundles which pass obliquely 

 into the base of the leaf, arranged in different number and order according to the position 

 of the section. The vascular bundles of the stem are weak compared to the mass of 

 the parenchyma, in transverse section they are roundish or flattened externally and 

 internally (Fig. 133). 



According to the numerous investigations of Hofmeister, Stenzel, and Mettenius, 

 fundamentally the same structure— even the narrow, reticulate bundles, which are weak 

 in arborescent stems— is found in Onoclea, Struthiopteris, in all investigated species 

 of Blechnum (inch Lomaria), Woodwardia, Asplenium, Phegopteris, species of Aspidium 

 with a stem having leaves in more than two rows, in Ophioglossum, and Aneimia. The 

 individual peculiarities depend partly upon the form of the meshes corresponding to the 

 elongation of the internodes— thus very elongated meshes are found in the runner-like 

 branches of the rhizome of Struthiopteris, Aspidium cristatum, in the creeping stems of 

 A. Thelypteris, quite short and broad ones in Aspl. Filix foemina— partly upon the 

 number and arrangement of the leaf-bundles which arise from the margin of a gap. Most 



' A. Braun, Schuppen d. Tannenzapfen, Nova Acta Leop. vol. XV. p. 278. 

 '' Hofmeister, Beitrage II. — Stenzel, /. c. 



