40 



PRINCIPLES OF PLANT-TERATOLOGY. 



There may be mentioned a quite distinct type of 

 fasciation, which involves suppression or transforma- 

 tion of the flower itself due to great vegetative develop- 

 ment of the pedicel. In the ash (Fraxwus excelsior) 

 there is a disease, due to the mite Phi/toptus fraxini, 

 which causes fasciation of the tips of the pedicels 

 while the flowers appear as curious swollen knobs. 



The same kind of thing, in which, at the same time, 

 the whole inflorescence becomes greatly hypertrophiecl, 

 involving very copious branching of the pedicellar 

 system, and in which the flowers are completely sup- 



Fig. 68.— Chrysanthemum segetum (Corn Marigold). Bifurcation of 

 capitulum, showing two stages. (Diagrammatic.) 



pressed, has given rise to the variety of the cabbage 

 known as the cauliflower (Brassica oleracea botrytis). 



The capitulum or " head " of a chrysanthemum 

 may either simply bifurcate more or less completely 

 (fig. 68), or it may fasciate, forming a flattened more 

 or less transversely-elongated head, in which no 

 division into separate heads is at all manifest, the disk- 

 florets being continuous right across (fig. 69) ; and, 

 under such circumstances, it is usually, owing to 

 inequalities of growth in the stalk below it, contorted 

 and bent in more than one plane in a most complicated 

 manner. The central continuous area of disk-florets 



