CHARACTERISTIC FORMS OF LEA FES AND SHOOTS. 1 99 



side with displacement of the mother-leaf, this would repeat diagrammatically in a 

 simple manner the branching and phyllotaxis of Datura ^. 



Still more complicated are the relationships in Fig. 150, where 1 represents the lower 

 part of a flowering plant of Herminium Monorchis ; 1 1 \s the surface of the ground, and 

 what lies below this is therefore underground. 5 is a swollen spherical root, above which 

 the leaf-forming shoot rises, which produces in its lower part slender lateral roots, «iu, w, oc, 

 as well as a sheath-like scale'- b, and two foliage-leaves c, d, and continues higher as a 

 slender scape Jl, bearing a raceme of flowers at its summit. Turning our attention 

 exclusively to the structure H; we find it to be a shoot which contains the bud for the 

 next year ; for the whole plant A, B, in / dies off" after flowering, a similar plant being 

 produced the next year from the bud contained in H. H is therefore an axillary shoot 

 of the scale b, an earlier condition being represented in Fig. ///, where M represents 

 the base of, the leaf b cut through its median plane; ^ is a fibro- vascular bundle 

 runjiing from the primary axis to the bud u; bl is the first leaf of this bud u which 

 is placed with its back to the mother-axis and forms a diminutive sheath enclosing 

 the succeeding leaves of the bud u ; B' is the young tuberous root with its root-sheath 'v. 

 In order to understand the displacement which has already taken place, the whole lower 

 part between M and u must be imagined shortened to such an extent that B'^ would be 

 somewhere near the letter g ; and the bud u must be supposed at the same time moved 

 backwards towards 0. By this means the normal position of the parts of H under con- 

 sideration is restored, and it is intelligible that the channel /, which the base of the leaf bl 

 encloses, is a consequence of the oblique direction outwards of the growth of the tissue 

 lying between and u, that the root-sheath v must be regarded as a part of the surface 

 of the primary axis above M, and that in consequence B'^ has been formed in the 

 tissue of the mother-axis beneath the bud «, and laterally on the fibro-vascular bundle g. 

 In the normal position of the bud and root, the axis of growth of the latter would form 

 almost a right angle with that of the bud, whereas by the displacement one forms a 

 prolongation of the other. The grow th of the mass of tissue lying between g and u now 

 advances in the direction named, and the whole lateral shoot assumes the form repre- 

 sented in H (Fig. /) ; the still further change of position of the parts which takes place 

 in consequence is explained by ¥\^. II, where kn represents the bud designated in /// 

 by «, bl the still more elongated sheath of the leaf bl in III; the channel / is the cavity 

 of the leaf bl increased in breadth, and which, were there no displacement, would be 

 entirely filled up by the bud u (or hi). 



In order to make the following displacement which occurs very commonly more 

 intelligible, reference should be first made to Fig. 108 (p. 133). This shows how the 

 tissue beneath the apex extends to such a degree by a very considerable early growth 

 in thickness, progressing equally in all directions, that the surface of the punctum 

 •vegetationis, which would otherwise be conically elevated, becomes almost level. The 

 apical point thus comes to lie in the middle of a plane instead of at the point of a 

 cone. In Helianthus this state of things remains nearly unchanged as the capitulum 

 developes; but the abnormal growth increases in many cases to such an extent that 

 the apical point eventually lies at the base of a deep hollow, the walls of which 

 result from older masses of tissue which properly lie beneath the apex, growing 

 upwards, and overarching the apex itself. This occurs, for instance, in the formation 

 of the fig, which, as shown in Fig. 151, is a metamorphosed branch, the apex of 

 which is at I^ still nearly level, at // has already been outstripped by a circular 

 leaf-bearing cushion, and at III^ is depressed in the form of an urn. The apical 

 pomt of this shoot lies in this case in the deepest part of the hollow, the inner side 

 of which is properly only the prolongation of the outside of the fig, and bears m 



^ [See Payer, Elements de Botanique, p. 1 1 7.] 



2 A first scale in the axil of which the bud k stands is no longer to be seen. 



