THE ANGIOSPERMAE : STEMS 



945 



Fasciated Stems. 



While it is not our intention to enter upon the bewildering study of 

 plant abnormalities known as Terat- 

 ology, there is one such abnormality 

 of stems which w-e shall mention be- 

 cause of its frequent occurrence and 

 striking appearance. It is that called 

 fasciation, which consists of the de- 

 velopment of a strap-shaped structure, 

 often several inches broad, in place of 

 a normal stem. Fasciated stems have 

 a " growing line " instead of a growing 

 point (Fig. 935). They often carry 

 hundreds of leaves and enormous num- 

 bers of flowers. A second type, called 

 ring-fasciation, transforms the stem into 

 a wide cylinder, open at the top and 

 lined with an internal as well as an 

 external epidermis. A complete explana- 

 tion of the morphology of these mon- 

 strosities is not available, but there are 

 two theories, one being that there has 

 been an enlargement of a single growing 

 point and the other maintaining that 

 there has been a congenital fusion of 

 many shoots. Worsdell, in supporting 

 the latter theory, claimed that it was 

 due to a recrudescence of the primitive 

 form of branching, dichotomy, otherwise 

 scarcely known among Angiosperms, with 

 the concrescence of the numerous shoots 

 thus produced. 



Biologically there are two types of 

 fasciation, one which is germinal and 

 inherited and another which is somatic 

 and non-heritable. Outwardly they are 

 indistinguishable, but there is some 



evidence that the latter type is stimulated by insect damage to the 

 growing point. 



Fig. 935. — Forsythia siispenso. Upper 

 part of a fasciated shoot. 



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