BUDS ON LEAVES. 43 



that give rise to buds; in other plants, particularly in the Gesneraeese, in the 

 species of Pepero'ynia, a genus belonging to the Pepper order, in Tournefortia, 

 Citrus, &c., it is cells of the callus that divide and become the rudiments of 

 buds, and indirectly of shoots. In the case of Begonias isolated buds occasionally 

 spring from the callus in addition to the others, but this is not inconsistent with 

 the fact that in these plants the epidermal cells are the favourite places of 

 inception. Especially are those epidermal cells preferred which are situated above 

 the bifurcation of a vascular bundle in the lamina. If an entirely uninjured leaf 

 is laid upon moist sand, the buds develop just above the base of the lamina 

 where the strands radiate out from one another. It is a common custom of 

 gardeners, however, when making use of Begonia-leaves to propagate the plant, 

 to set the petiole in wet sand and to make a number of transverse cuts across 

 the larger veins of the lamina, which is laid flat upon the sand. After this 

 operation quite a host of buds — i.e. new plants — take their rise all along the 

 course of the intersected vein, some immediately in front of the cut, which 

 is covered by a callus, but frequently others again at a distance from that 

 spot. From this we may conclude that the new formation depends principally 

 upon the conduction of material by the veins. No doubt its relative position 

 with regard to the roots developed from the callus to the stock of reserve 

 materials and so forth, also play an important part. The upshot is, however, 

 that numberless cells of the epidermis of the leaf become the seats of inception 

 of new plants, and that buds are able likewise to develop from deeper-lying 

 cells of the callus. Whether the development of an epiphyllous bud has begun 

 in one place or another, there is always in the inceptive area a concomitant pro- 

 duction of vascular bundles, which establish a connection between the axis of the 

 bud in process of formation and the previously-developed roots; and it is not 

 long before the axis produces green foliage-leaves capable of assimilating in the 

 presence of light. The leaf-cutting, upon which a miniature plant is now seated, 

 in most cases retains its vitality for a considerable time longer, but at length 

 it begins to turn yellow and gradually it dies. Only that part which produced 

 the buds and roots persists in the form of a pad, forming in some species, for 

 example, in Begonias, a thick, fleshy, cellular body, looking almost like a little 

 tuber. 



The phenomenon above described as ensuing in consequence of artificial 

 manipulations takes place sometimes spontaneously in nature in a few plants, and 

 that without the leaf concerned in the process being separated from the axis. Ex- 

 amples of plants which have been observed to bear occasional epiphyllous buds when 

 growing wild in their natural habitats are Cruciferse {Cardamine pratensis, 

 Nasturtiwni officinale, Roripa palustris, Brassica oleracea, Arabis pumila), 

 Papaveracese {Ghelidonium majus), Water-lilies (Nyniphcea guianensis), Gesneraceae 

 (Episcia bicolor, Chirita sinensis), Lentibulariese {Pinguicula Backeri), Aroidese 

 {Atherurus ternatus), Orchidacese (Malaxis monophyllos and M. paludosa), 

 Liliacese {Fritillaria, Ornithogalum, Alliwin, Gagea, Hyacinthus) and Amaryllidese 



