250 The Phenomena of Morphogenesis 



Luffa, Kowalewska ( 1927 ) shoots from Phaseolus and Visum, and Carlson 

 (1953) only roots from Raphanus and Brassica. La Rue (1933) reviewed 

 work on this subject and reports his own success in obtaining roots on 

 excised cotyledons of 19 species and shoots on those of 22 species. 



Several investigators have studied regeneration in inflorescences. If this 

 structure is cut off and treated as a cutting, root formation and subse- 

 quent vegetative development of the inflorescence often follow. Bor- 

 mann (1939) reviewed the literature and made extensive investigations 

 himself, finding that, of 391 species studied in 65 genera and 45 families, 

 the conversion of an inflorescence into a vegetative shoot by treating it 

 as a cutting occurred in about 17 per cent of all the species. 



Flower cuttings of Cactaceae, where the stem is incorporated into the 

 fruit, have been found to form roots and develop dormant buds ( Goebel, 

 1908 ) . The ovary of Jussiaea as well as immature fruits of Lecythis react 

 in the same way. Carriere (1877) describes the rooting of the capsule of 

 Lilium speciosum and Kupfer (1907) that of pods of Plwseolus. 



La Rue (1942) found that, under favorable cultural conditions that 

 provide both moisture and food, many flowers or their parts may be 

 induced to root ( Fig. 9-7 ) , and by this means he obtained roots on flow- 

 ers of three genera of monocotyledons and 22 genera of dicotyledons. He 

 went further and was able to induce regeneration even in gametophytes. 

 Female gametophytes of Zamia in sterile culture not only increased in 

 size markedly but in a few cases developed small roots and buds. The 

 latter produced leaves resembling miniature seedling ones. He later 

 obtained similar results with Ctjcas (1954). 



Reproductive Regeneration 



The ability of a part of the plant to restore missing structures and 

 thus regenerate a whole is essentially the ability to reproduce. Regenera- 

 tion is a reproductive process, and it is understandable that during the 

 course of evolution many plants should have developed means to use 

 the totipotency of their individual cells and tissues as means for vege- 

 tative reproduction. In many cases this has become a normal and spon- 

 taneous process, as in the formation of foliar embryos on the leaves of 

 many Crassulaceae or of bulbils in other forms. Isolation or injury may 

 stimulate the growth of similar structures, and this process thus grades 

 over into regeneration. In many cases it is difficult to distinguish be- 

 tween the two. 



This type of reproduction has been described most commonly in 

 leaves and leaf cuttings (Fig. 9-8). Many cases have been studied in 

 both dicotyledons and monocotyledons. Goebel cites a variety of these 

 from the earlier literature. In some cases plantlets occur naturally on 

 leaves and drop off to form new individuals (gemmipary). In others 



