146 THE PLANT WORLD. 



mais. There are other forms which are '^susceptible" and which 

 respond to the traumatic stimuhis, but these are the ones to wliicli 

 particular attention has been directed. 



Over against these experiments emphasizing the results of 

 mechanical interference lies tlie series carried on by deYries* on 

 the influence of environment upon fascination. Eich fertiliza- 

 tion, plenty of light, space and air, tlic time of the year, and care 

 in ])lanting may all be utilized in producing increased nund)ers 

 of fasciated stems. Husf coiitv<)llc(1 the water supply and the 

 nutrition in such a way as to regulate tlio a])pearance of fascui- 

 tion in ten or more species, and numbers of interesting observa- 

 tions have been made as to the apparent effect of rainy seasons 

 and other environmental factors on its prolific occurrence. Tn 

 this connection, however, it must be remembered that the influ- 

 ence of many co-existent factors has not been eliminated, so that 

 the actual causal relation between these plienomena is undem- 

 onstrated. 



Aside from the artificial production of fasciation tlivough 

 injury its natural derivation from the same cause might be ex- 

 pected. A nasturtium seedling whose top dies back may fasciate 

 just as if it had been rudely pinched or bruised. The various 

 tearings and breakings to which plants are subject or the destruc- 

 tion of parts through the influence of fungi may also stimulate 

 fasciated development of the latent growing regions. By far 

 the most common source of disturbance, however, is to be found 

 in the insects which are constantly visiting the plants, and which 

 often live parasitically upon them for the greater portion of their 

 existence. The creatures frequently ])ierce the young parts with 

 their ovipositors, or in the larval stage with their mandibles, 

 while feeding upon the tissues. Womids of such a character arc 

 what produce fasciation in the evening ])riiiiroses, and the vari- 

 ous forms of fasciated stems oavc their origin to this stimulus. 



Examination of species of (Enothera by cutting or splitting 

 the axes, reveals within many of them comparatively large num- 



■"cleVries, H. Die ]\rntatio]is-Tlio<)iie. Loi)izi<i-, 1001. 

 tHus. H. Fasciation in O.mlis crenata and Experimental Production 

 of Fasciation. Kept. Miss. Bot. Gard. 17:157,7900. 



