DIFFERENT ORIGIN OF EQUIVALENT MEMBERS, 



175 



the Hepaticae Radula and Lejeunia; the branch springs (as shown in Fig. 116, z, p. 153) 

 out of the lower part of a segment of the stem, the upper part of which has developed 

 into a leaf. In Fontinalis this occurs below the median line of the leaf, in Sphagnum 

 laterally below one half. According to the same observer, the lateral branches arise 

 in place of a half-leaf beside the remaining half in many Jungermanniese, as Frullaniay 

 Madotheca, Mastigobryum, Jungermannia tricbophylla \ If each tooth in the leaf-sheath 

 of an Equisetum be considered as a leaf, the buds originate at the side of the leaves and 

 between them, for they break through the leaf-sheaths between the teeth. In Gharaceae 

 and Angiosperms the normal lateral branchlets spring from the acute angle which the 

 leaf forms with the stem (Figs. 129, 131). Usually only one is formed above the middle 

 of the insertion of the leaf, or two or three one above another; sometimes several 

 are formed side by side, as in the bulbs of Muscari (Fig. 130), and the flowers in the 

 axils of the bracts of Musa. Such branchlets are called Jxillary Shoots; in Angio- 

 sperms the branching is, with a few doubtful exceptions, always axillary'^ 



The axillary shoot is usually so situated that it is attached both to the Subtending leaf 

 in the axil of which it grows and to the primary axis, and is therefore in direct con- 



FlG. 131. — Apical region of a primary axis 

 oi Dictatnnus Fraxinella, seen from above; 

 J apex of the primary axis ; b b b the young 

 leaves ; k k their axillary buds, the two young- 

 est leaves have not yet axillary buds. 



Fig. 132.— Young inflorescence of Isaiis 

 taurica, seen from above ; s apex of the 

 axis of the inflorescence ; the flower buds 

 appear beneath it (in whorls of four) ; the 

 youngest are still simple leafless elevations. 



nection with both. But it is not unusual for the lateral shoot to advance along the 

 primary axis and thus lose its connection with the subtending leaf ^, or contrariwise to 

 appear as if attached to the base of the leaf away from the axis. Examples of both are 

 furnished by the sporangia of Lycopodium and Selaginella. The advance of the axillary 

 shoot along the base of the subtending leaf is not uncommon in the inflorescence of 

 Phanerogams, where the flower-bud springs from the base of the bract, as in Hippuris 

 (Fig. 119, p. 155), Amorpha, Salix nigricans, Sedum Fabaria, &c. But, on the other 

 hand, the subtending leaf may advance on its axillary shoot, when it originates later than 



Lkad. der Wissen. zu Wien, vol. LVII, 1868, and vol. LIX, 1869 ; and Bot. Zeitg. 1871, no. 34. See 

 Iso more in detail, Book II, Muscinese. 



^ Leitgeb, Bot. Zeitg. 1871, p. 563 ; see also Book II, Hepaticre. 



^ [The relationship of leaf and lateral shoot is intelligible in the Muscine<£, where the two struc- 

 ires are derived from the same ultimate segment of the apical cell. In Phanerogams Warming 

 'considers (/. c. p. xxiii) the leaf and its axillary bud (which are always united at their base) to no 

 less form a whole, and to constitute a double organ whose parts have a different morphological 

 value and are sometimes equally developed, while in some cases one is developed at the expense of 

 the other.] 



^ [This occurs not unfrequently in the flowering shoots or inflorescences of Phanerogams, when 

 such shoots are termed extra-axillary. '\ 



