90 



PRINCIPLES OF PLANT-TERATOLOGY. 



concentrically-grouped sets : an external, normally- 

 orientated, and an internal, inversely-orientated set 

 (fig. 26). This phenomenon, which is not an un- 

 common one, occurs in the stem of the so-called 

 " mummy pea " (Plsum sativum var.) in which the 

 fasciated condition always comes true from seed. 

 Boodle, also, has noted it in shoots of the hollyhock 

 {Althaea rosea), and Conard in those of the yam 

 (Dioscorea Batatas). Schoute has also observed it in 

 the stems of some abnormal palms. Somewhat more 

 complicated instances have been noted in the scape 

 of the dandelion (Leontodon Taraxacum) by Reichardt, 

 Michelis, Cramer, and others. In the case of Reich- 

 ardt's specimen the scape bore four capitula around 

 the apex, in the centre of which an aperture gave 

 entrance to the central cavity of the scape, which 

 gradually narrowed below, ending blindly some way 

 down. Besides the normal central cylinder of the 

 scape, there were two inner rings of bundles, the 

 innermost of which ended blindly (passing from below 

 upwards) in the solid core just below the narrowed 

 termination of the cavity. Unfortunately this author 

 says nothing about the orientation of the bundles 

 composing these rings : a most important feature. He 

 regards this remarkable phenomenon of the abnormally 

 swollen scape, with its four capitula, central cavity, and 

 three vascular cylinders, as due to a fusion of five 

 scapes, a central rudimentary and four peripheral ones; 

 and he gives an ingenious reason for his belief ; but this 

 explanation is on a par with that of fusion, so often 

 ascribed to the phenomenon of ordinary fasciation, and 

 is not really adequate (see below). 



What is said with regard to the interpretation of the 

 general phenomenon of fasciation may be so far fore- 

 stalled by stating that ring-fasciation, like ordinary 

 fasciation, may be regarded as an attempt on the part 

 of the cylindric organ to effect a multiple dichotomy. 

 In many cases, possibly in all those which concern 

 cylindric structures, this is primarily induced by an 



