576 SPECIAL PLANT PATHOLOGY 



f ul flowers. Here too are concerned sharp contrasts occurring suddenly. 

 Either the plants (usually set in peat soil) in summer are left too dry, and 

 later watered very abundantly, or they are brought too suddenly into 

 the warm house in the autum. In both cases the leaves are weak func- 

 tionally and then their functioning is increasingly stimulated by the 

 increased upward pressure of the water. If the transition is brought 

 about gradually, the inactive leaf Surfaces would have time to resume 

 their normal action by a general slow increase in their turgidity and 

 there would be no resultant injury. But, with the sudden upward 

 pressure of the water, the basal region alone is stimulated, thus causing 

 the development of the cleavage layer." Here are briefly a few of the 

 observations of the writer on two plants of Ftuhsia brought into the 

 house from out of doors and placed in a window with a bright southern 

 exposure. Soon after removal to the house although abundantly 

 watered the leaves began to drop until the window sill was covered with 

 the litter. New leaves were constantly formed, but these in turn 

 dropped off and this phenomenon continued through the winter until 

 the plants were transplanted the following summer to garden soil when 

 the dropping of the leaves ceased and the plants again became apparently 

 normal. The general concensus of opinion among plant pathologists is 

 that the disturbance in the equilibrium of the turgor distribution is the 

 cause of all premature dropping of the leaves. "For house plants it 

 may*be recommended as a fundamental principle that the plants should 

 be subjected gradually to other vegetative conditions, and the dormant 

 period, upon which every vegetative part enters, should not be inter- 

 rupted by an increase in the supply of heat and moisture." 



Curly-dwarf of Potato. — This is a peculiar disorder characterized by 

 a dwarfed development of the potato plant accompanied by a curling 

 and wrinkling of the foliage, so that it resembles the foliage of the va- 

 rieties of cabbage known as Scotch Kale and Savoy Cabbage. The 

 Germans call it Krausel Krankheit. The disease is manifest in the 

 shortening of the leaf petioles, midribs and veins of the leaves and es- 

 pecially in the nodes, so that the foliage is clustered thickly. The 

 diminished growth of the veins in proportion to the cells of the funda- 

 mental tissue results in a wrinkled leaf surface, often curled downward. 

 There seems also a tendency for the formation of a greater number of 

 secondary branches, associated with brittle stems. The color of the 

 foliage is not altered as it remains a normal green except in very severe 



