CONNECTION OF THE BUNDLE-SYSTEMS. 315 



case has been observed ^, in S. Kraussiana ^ both cases are found ; in the latter there 

 is also a more or less complete transverse anastomosis at the point of branching. 

 The passage into the lateral shoots has not been exactly investigated in those Sela- 

 ginellse which have several bundles in their shoots. 



2. Adventitious Shoots. 



Sect. 97. It is a general rule for adventitious shoots that their bundle-system is 

 always inserted on those vascular bundles, or points of the wood or bast body of the 

 main axis, which are nearest to their point of origin. Since such shoots may arise 

 at the most heterogeneous points, and at the most various periods of the life of the 

 plant, the individual cases show great variety. If the normal course of the bundles 

 is known, their relative arrangement is completely determined by what has been said 

 above. 



II. ROOTS. 



Sect. 98. In the forked roots of the Isoetese, Selaginelte, and Lycopodia, the 

 vascular bundle forks as in dichotomous stems. 



Roots are found as lateral branches on members of their own kind, as well as 

 on stems, rarely on leaves' ; some appear in definite morphological positions, e. g. at 

 definite points of the leaf-insertion ; others are without arrangement : the former may 

 be called normal, the latter adventitious lateral roots. 



The invariably endogenous formation of lateral roots takes place in or close to 

 vascular bundles or masses of wood or bast. Their vascular bundle is inserted 

 directly and without branching on the nearest one of the main axis, or it divides into 

 branches, which connect themselves with several bundles of the axis. 



The former simple insertion occurs obviously in members with a simple axile 

 bundle — thus in almost all roots ; also in stems constructed on the Dicotyledonous 

 type, and in the Ferns. 



Splitting of the bundle of the root into several shanks, which insert themselves 

 on several bundles, is a common phenomenon in the stem of Monocotyledons. It 

 does not occur however in all species ; e. g. in the rhizome of Carex hirta each root- 

 bundle inserts itself simply on one peripheral bundle of the stem-cylinder. 



The branches or shanks, into which the root-bundles about to be inserted are 

 divided, separate at the periphery of the bundle-cylinder, they then insert themselves, 

 in a first series of cases on the bundles which are present at that point, without 

 penetrating more deeply into the cylinder of the stem : this is the case in the 

 investigated Orchidese, many Commelinea;, Aroidese, Richardia sethiopica, Philo- 

 dendron spec, with few short shanks, diverging chiefly upwards and downwards ; 

 Acorus with more abundant branching ; Calla palustris * with a ring of roots, whose 

 bundle-insertions together form a transverse girdle at each node of the rhizome. 



' Compare Nageli \mi Leitgeb, Entstehung, &c. d. Wurzeln, Taf. XVIII. Fig. 11. 

 " Hofmeister, Vergl. Unter. Taf. XXIII. p. 4. 



2 [Compare Mangin, Origine et Insertion des racines adv^ntives . . . chez les Monocotyledones, 

 Ann. Sci. Nat. ser. 6, torn. 14, 1882.] 



* Van Tieghem, Stnict. des Aroid^es, /, c. 



