28 



BUDS ON STEMS. 



folia, and to various species of Acacia, Halesia, Hermannia, and Plumbago. More- 

 over, the development of buds on roots is observed to take place not only in trees 

 and shrubs, but also in herbaceous plants; and, indeed, in some it is of regular, 

 annual recurrence. As instances of this may be mentioned the Dwarf Elder (Sam- 

 bucus Ebulus), Asclepias Cornuti, Sophora alopecuroides, Lepidium latifolium, 

 the Dock (Rumex Acetosella), various species of the Toad -flax and Spurge (e.g. 

 Linaria pallida, L. genistcefolia, L. vulgaris, Euphorbia Cyparissias), and several 

 Composites and Pelargoniums. In another series of herbaceous plants the pheno- 

 menon occurs exceptionally as a result of special external conditions, and chiefly in 

 consequence of injuries, as, for example, in case of damage to the roots of certain 

 Orchids {Epipactis raicrophylla, Neottia Nidus -avis), or of the Adder's Tongue 

 amongst Ferns (Ophioglossum vulgatum). Nor must we omit to mention the buds 

 which are formed on aerial roots. There is so regular a production of buds from the 

 columnar aerial roots of tropical Fig-trees, and of leafy shoots from the buds thus 

 developed, that at first sight one is inclined to take the root-columns for trunks. 



BUDS ON STEMS. 



Buds and shoots growing directly from a part of the stem are termed cauline 

 buds and shoots. Any part of a stem may become the point of inception of a bud. 

 The commonest positions occupied by buds are the regions of the stem which bear 

 respectively scale-leaves and foliage-leaves, and this is especially the case with those 

 buds which subsequently become brood-bodies. But also lower down and higher 

 up buds are observed to develop, and do so, indeed, without the occurrence of any 

 apparent injury or other assignable external cause. Thus, for instance, it frequently 

 happens that buds are developed on the hypocotyl of the Scarlet Pimpernel (Ana- 

 gallis arvensis), which abounds in our fields and kitchen-gardens, and the- same is 

 true of the species of Spurge {Euphorbia Peplus and E. vulgaris) which grow as 

 weeds in company with the Pimpernel, and likewise of yoimg Toad-flax plants 

 {Linaria vulgaris), and of a few Umbellifers. These buds grow out immediately 

 into green leafy shoots. In all probability the phenomenon occurs in many other 

 plants besides, but hitherto the subject has received only cursory attention. 



These buds on the hypocotyl are all the more worthy of notice because they 

 emerge below the cotyledons and in no case from a leaf-axil, i.e. the angle formed 

 by a leaf with the stem. In the region of the foliage-leaves it is comparatively rare 

 for a bud to originate at any other spot than in the axil of a leaf. , As instances 

 may be mentioned the extra-axillary buds of the Nightshades (Solanaceae), the buds 

 in Serjania, Medeola asparagoides, &c., which spring laterally from the stem close 

 to the foliage-leaves, and those in the Vine and Virginian Creeper (Ampelidese), 

 which are set opposite to the foliage-leaves. But even in these cases the positions 

 of the buds, relative to the foliage-leaves of the stem, are always such as to be 

 most naturally explained by the need of the former to obtain the formative materials 

 produced in the green tissue of the leaves, in order to complete their own develop- 



