DIFFERENT ORIGIN OF EQUIVALENT MEMBERS, 



173 



known are those which are formed abundantly in the indentations of the leaves of 



Bryophyllum calycinum ; according to Hofmeister^ they arise before the complete un- 



ifolding of the leaf as small masses of primitive parenchyma in the deepest parts of the 



incisions of the leaf. In the aquatic Utricularia 'vulgaris weak shoots arise, according 



to Pringsheim^, mostly in the neighbourhood of the axils of the divisions of the leaf; in 



)th cases these shoots are of exogenous origin. Nothing is known of the develop- 



lent of the buds produced on the leaves 



)f Atherurus ternatus or Hyacinthus Pouzohii 



[(Doll, Flora von Baden, p. 348). 



(b) Adventitious shoots springing from 

 [Roots are always endogenous; they arise, 

 [according to Hofmeister, in the neighbour- 



lood of the fibro-vascular bundles or in the 

 :ambium, as in Ophioglossum, Epipactis mi- 

 trophylla, Linaria "vulgaris, Cirsium ar'vense, 

 the aspen, and apple. 



(c) Adventitious Buds arise moreover 

 iin an endogenous manner under peculiar 

 ^circumstances from older detached leaves 



or pieces of stem and root, especially when 

 ;kept damp and in darkness. On this de- 

 ^pends the propagation of many plants in 



gardens, as of Begonias from leaves, Marat- 



tias from their thick stipules, &c. Adven- 

 [titious buds also sometimes appear in con- 

 fsiderable quantity in old stems of woody 

 ; plants ; this occurs on the callus formed 



between the bark and the wood, when 



the stem is cut off above the root. The 



branchlets which break out in old stems 



of Dicotyledons and Monocotyledons are, 



however, often not true adventitious shoots, 



but old dormant * eyes' which have been 



left behind, having been formed at an 



earlier period as normal exogenous axillary 



buds, when the stem itself was still in the 



bud-condition ; they had become enveloped 



by the bark as the stem increased in thick- 

 ness, and carried on a feeble existence, 



until placed in a condition for active 



growth by a favourable accident, as the 

 , removal of the stem above them (Hartig). 



(d) In the genus Iso'e'tes the leaf-bearing shoot arises exclusively from the fertilised 

 germ-cell or embryo, and forms neither normal lateral buds out of the stem nor any 

 from the leaves or roots, nor any kind of adventitious buds. 



(e) The Normal Formation of Lateral Shoots from the primary meristem of the growing 

 point of the primary axis is endogenous in Equisetaceae ^. With the exception of the 



-primary axis which is developed out of the embryo, all the lateral shoots are here of 



Fig. i2B.—Eguis€tu>n arvetise; longitudinal section through 

 an underground bud in March ; ss the apical cell of the stem ; 

 b—^b its leaves ; K K' two endogenous lateral buds exposed by 

 the section. The youngest rudiments of buds are to be found, 

 however, at b", amd they have probably begun to be formed 

 even at a greater height (x 50). 



J69. 



* Hofmeister, Allgemeine Morphologie, p. 423. 



^ Pringsheim, Zur Morphologie der Utricularien ; in Monatsb. der k. Akad. der Wissen. Berlin 



[Some doubt is, however, now thrown on this exception ; see Book II, Equisetaccoe.] 



