the Sweet Poiato. 2 1 3 



The two doubtful cases of ring-fasciation are : First, a 

 "tubular stem of Sempo'vivum'" recorded by Masters (12), 

 and, second, two fasciated sweet-peas with " large tubular 

 stems," reported by C. P. Qualch(i9) ; from inside the hollow 

 of each of these arose a single stem, partly free and partly 

 adherent. Probably all of these were cases of ring-fascia- 

 tion. 



Concerning Michehs' dandelions (14, 15), Nessler is doubt- 

 less right in considering them as fusions, and belonging to 

 quite another category. Neither can we get much light on 

 the present subject from normal structures, as the fruits of 

 Ficus or the " hips " of roses, for in these the morphological 

 apex of growth lies in the bottom of the cup-like body. The 

 occurrence of two of the three true ring-fasciations in fasciated 

 races, namely, Veronica longifolia and sweet potato, and the 

 frequency of ring-fasciation and abundance of plain fascia- 

 tion in the latter plant, make it highly probable that the 

 two phenomena are but phases of one and the same con- 

 dition. The very frequent splitting of the tubes into one 

 to three or four bands makes the correctness of this view 

 almost certain. An injury to the growing tip has been 

 suggested as a cause of ring-fasciation, but no sign of such 

 has been found in any of the cases examined. We may 

 therefore consider that whereas plain fasciation occurs when 

 the meristem is so stimulated (by overfeeding or otherwise) 

 as to cause it to spread out in two opposite directions and 

 become linear at the apex, ring-fasciation occurs when the 

 same stimuli, operating for a time in radial symmetry, cause a 

 spreading of the meristem in all directions equally, giving rise 

 to a circular apical region.^ 



^ Since going to press two ring-fasciated shoots have appeared on a plant of 

 Symphytum caucasicutHy growing in the University Botanic Garden. 



