877 



organs. The adventitious buds are always found on the upper surface 

 where the woody part of the vascular bundles is turned toward the upper 

 side of the leaf; they are produced in the axes of the ribs and are usually 

 more strongly developed the thicker the vascular bundles. The roots are 

 produced from the phloem side of the vascular bundles. 



RegeP enumerates the plants on which buds of leaf origin have been 

 observed. A few examples may be named here since the buds develop 

 their own roots after having been carefully removed from the leaf and, 

 therefore, are of importance in propagation. Besides the well known 

 Bryophyllum calycinum, which Berge- studied and on which incisions 

 between two serrations of the leaf develop a meristematic tissue in an early 

 stage and from this meristem buds, the following species are noteworthy: 

 Hyacinthus Pauzolsii, Fritillaria impcrialis, Omit hog alum thyrsodies, 

 Drimia, Malaxis, Cardamine, Nasturtium, Brassica oleracea, Ranunculus 

 bulbosus, Chelidonium majus, Levisticum offic, Ultricularia, Begonia quad- 

 ri-color, B. phyllomaniaca'-^. Hansen* mentions also Hippuris, Elodea 

 canadensis and other water marsh plants. Caspary" mentions Nymphaea 

 micrantha and its hybrids. He also cites examples in which an inflorescence 

 developed instead of a leaf. In this way the upper side of the petiole of a 

 cucumber (Cucuniis sativus) was covered with more than 120 staminate 

 blossoms without a single vegetable leaf. 



The success of propagation by leaf cuttings depends upon the indi- 

 viduality of the leaf as well as upon the plant species. Very young leaves 

 must be excluded because of the immaturity of their tissue systems ; very 

 old ones because of their scanty life energy and the ripeness of their chloro- 

 phyll apparatus. 



According to Lindemuth's'^ observations, in genera where the leaves can 

 be used as cuttings, the plants thus produced are on an average stronger 

 than those from wood cuttings. As soon ^ as a leaf has developed a few 

 roots, it may be considered a new individual, even when it is not able to 

 produce shoots. This arises from the capacity of such leaves to live longer 

 than unrooted ones and GoebeF could also prove an increased growth in 

 thickness (in Bryophyllum). Lindemuth also observed, in a begonia, that 

 a flower shoot can be formed instead of foliage shoots in leaf cuttings. This 

 circumstance might indicate that the leaves furnish different products of 

 assimilation at different ages and places on the axis. Usually the assimilates 

 capacitate the bud, produced on the leaf cutting, to form only foliage shoots. 



1 L.OC. cit, p. 452. 



2 Beitrag-e zur Entwicklungsg-eschichte von Bryophyllum calycinum. Zurich 

 1877; cit. Bot. Jahresber. rv, p. 423. 



^- Mohl, t^ber die Cambiumschicht des Stammes der Phanerogamen und ihr 

 Verhaltnis zum Dickenwachstum desselben. Bot. Zeit. 1858, p. 196. 



4 Log. cit., p. 1002. 



■'■' Casparv, Bliitensprosse auf Blattern. Schriften d. phys.-okonom. Gesellsch. 

 XV, 1874, p. 99. 



6 Lindemuth, H., Weitere Mitteilungen iiber regenerative Wurzel- und Spross- 

 bildung auf Laubblattern (Blattstecklinge). Gartenflora 1903, p. 619. 



7 Flora 1903, p. 133. 



