282 The Phenomena of Morphogenesis 



Certain instances of fasciation have received special study. It has long 

 been observed that if the epicotyl of a seedling of Phaseolus multiflorus 

 is cut off and the buds in the axils of the cotyledons are then allowed to 

 grow they will produce flattened shoots. These later revert to a cylindrical 

 form and produce normal branches. This is an unstable kind of fasciation, 

 and the factors responsible for it are not yet clear (Sachs, 1859; Klebs, 

 1906; Georgescu, 1927; Bausor, 1937). 



Fasciations resulting from other types of mutilations and from wounds 

 are discussed by Blaringhem ( 1908 ) . They frequently follow pruning in 

 Salix, Populus, Robinia, Tilia, and Corylus. 



Various other factors, both external and internal, have been found to 

 produce fasciation. Growth substances applied in high concentration may 

 induce such vigorous local growth that ribbon-like structures result 

 (Bloch, 1938). In strawberry varieties that have a tendency toward fas- 

 ciation, this is emphasized by short day-lengths ( Darrow and Borthwick, 

 1954). It has been suggested that fasciation is due to a high level of 

 nutrition, to insufficient nutrition, to changes in correlation produced 

 by growth substances, and to various factors that have been shown, 

 in both normal and regenerative growth, to induce correlative disturb- 

 ances. 



Of especial interest are those instances where fasciation, or a tendency 

 toward it, is inherited. The best known of these is in the cockscomb, 

 Celosia cristata, where the inflorescence is often much flattened. Heredi- 

 tary fasciation has also been found in Nicotiana (O. E. White, 1916), 

 Pharbitis (Imai and Kanna, 1934), and Phlox drummondii (Kelly, 1927). 

 The large-fruited varieties of tomato with more than two carpels may be 

 regarded as examples of genetic fasciation. 



Fasciation is found in all groups of vascular plants. Penzig ( 1921 ) has 

 reported it for Psilotum and Lycopodium; Kienholz (1932) for Pinus, and 

 Schenck ( 1916 ) for other gymnosperms. It is widespread in angiosperms, 

 both dicotyledonous and monocotyledonous, and many instances are cited 

 by Masters. It is particularly frequent in Taraxacum, Antirrhinum, and 

 Delphinium and has even been found in the giant cactus, Carnegiea 

 gigantea. 



Pelory. Pelory (or peloria) is a type of floral abnormality, quite dif- 

 ferent from the others that have been mentioned, in which dorsiventrally 

 symmetrical (bilabiate) flowers become radially symmetrical. It was first 

 discovered by Linnaeus in Linaria vulgaris, where it may frequently be 

 found in nature, and has been studied by Sirks ( 1915 ) and others ( Fig. 

 11-5). In this species peloric flowers, where they occur, are found at the 

 base of the inflorescence and may show a transition to normal ones at the 

 top. This is perhaps another instance of phasic development. Peloric 

 flowers have also been investigated in Linaria spuria, Antirrhinum majus, 



