398 



PRIMA RF ARRANGEMENT OF TISSUES. 



Coprosma ligustrina, Exostemma floribundum S Quercus^); from the anastomoses 

 at the node; or from the transverse curves, e. g. in those Rubiacese which have them, 

 as is seen in an especially striking way in the large leafy stipules of the Stellatae, 

 and in Sambucus Ebulus (Fig. 44), &c. 



In less common cases special lateral bundles of the composite leaf-trace, which 

 traverses the stem, pass into the stipules'. In Viola elatior one lateral bundle of 

 the three forming the leaf-trace passes into each stipule, and in addition branches 

 from curved transverse anastomoses, which appear in the node between the bundles 



of one trace. In Platanus occidentalis the 

 sheathing stipule has 7-9 bundles at its 

 base; of these the two stronger lateral ones 

 arise from the outermost lateral bundles of 

 the leaf-trace (which has 7-9 bundles), the 

 rest unite to two, sometimes to one or 

 three bundles, which separately enter the 

 bundle-ring of the stem. In Humulus 

 Lupulus ', of the three bundles of each 

 leaf-trace which enter the stem, the median 

 one passes into the petiole, and each lateral 

 one into a stipule as its middle nerve. 

 Each lateral one is connected at the node 

 by a transverse bundle on the one hand 

 with its median bundle, on the other with 

 the lateral one of another (opposite) leaf; 

 from the transverse girdle thus formed the 

 lateral nerves of the stipules are given off 

 in regular succession, so that the girdte 

 itself is compounded in a sympodial manner of outwardly curving bundles. 



Sect. 89. The bundles run as a rule straight through the petiole towards the 

 lamina. When they are numerous they are here also branched and connected by 

 anastomoses. The bundles, when more than one, are arranged on the transverse 

 section either in a curve open upwards, or in a ring, or distributed over the whole 

 surface of- transverse section. Large leaves, e, g. of Leguminosae, Umbelliferse, 

 Palmae, Aroidese, Cycadeae, Ferns, &c., yield various special examples of these 

 relations, which have been often made use of in the Ferns for systematic 

 purposes *. 



Sect. 90. In the lamina of leaves, whatever their form, in the peripheral leaf- 

 members of any stem, and in the leaf-like branches (Phyllodes, Phyllocladia, &c.), 



FIG. 144.— Sambucus Ebulus, after Hanstein. Scheme of 

 the bundle system in two successive internodes ; the cylindrical 

 surface reducedto a single plane. Leaves in decussate pairs ; 

 each leaf receives one median bundle. /(, and on either side 

 two lateral ones, s', s" \ of these the inner stronger one, j', 

 descend.s undivided into the internode : the outer one, s", 

 ■divides in the node into two shanks ; one inner one which 

 pursues a solitary course downwards, and an outer -which 

 coalesces at once witli the similar one of the opposite leaf (a). 

 By this union in the node the transverse girdle is formed, from 

 which the bundles n pafis into the stipules. The further course 

 of the leaf-trace of each pair, which consists of twelve bundles, 

 IS obvious on study of the figure. From Sachs' Textbook. 



' Hanstein, I.e. 2 A. B. Frank, Botan. Zeitg. 1864, p. 378. 



' Nageli, I.e. pp. 75, 92, 114. 



• Compare e. g. Grew, Anatomy, Tab. 49, — Presl, Gef assbiindelvertheilung im Stipes der Fame, 

 Abhandl. d, k. Bbhm. Ges. d, Wissensch. 5. Folge, Bd. V. — Reichardt, in Denkschr. d. Wiener 

 Academic, Bd. XVII.- Duval- Jouve, Et. sur le petiole des Fougferes, Hagenau, 1856. — Tr^cul, Ann. 

 Sci, Nat. 5 ser. X and XII, and the descriptive literature of Ferns. — Reichardt, Ueber d. centr. 

 Gefassbiindelsystem einiger Umbelliferen, Wiener Acad. .Sitzungsberichte, 1856. — A. B. Frank, 

 Botan. Zeitg, 1864, p. 380. [De CandoUe, Anatomie comparee des Feuilles, Geneva, 1879.] 



