258 DISEASE IN PLANTS. 



supplies of available food-materials ; but it should 

 be noted that conditions quite comparable to 

 proliferation are normal in the inflorescences of 

 Pine-apples, some Myrtaceae, Conifers, etc., and 

 that many instances of proliferations come under 

 the head of injurious actions of fungi, insects, 

 and other agents. 



Proliferatio7i of tubers is sometimes seen in 

 Potatoes still attached to the parent plant in 

 wet weather following a drought. The eyes grow 

 out into thin stolons, or forthwith into new tubers 

 sessile on the old tuber. Similarly in store we 

 sometimes find the eyes transformed directly into 

 new tubers, and cases occur where the growth of 

 the eye is directed backwards into the softening 

 tuber, and a small potato is formed inside the 

 parent one. 



Threading is also occasionally met with in the 

 *' sets " when ripened too rapidly in hot dry 

 soils. 



Vivipary is a particular case of proliferation, in 

 a certain sense, where the seeds appear to ger- 

 minate in situ, and we have small plants springing 

 from the flowers, reminding us of wheat which has 

 sprouted in the shocks in damp weather. In 

 reality, however, the grains are here replaced by 

 bulbils which sprout before they separate from 

 the inflorescence. In varieties of Poa, Polygonum, 

 Allium, Gagca, etc., this phenomenon is constant 

 in plants growing in damp situations. 



Proplesis. -It frequently happens that branches 

 or whole plants are suddenly defoliated in summer, 



