February, '14] SPAULDING: PLANT DISEASE INSPECTION 107 



drought, but there are some very serious fungous diseases which have 

 this symi3tom. 



Death of parts of the affected plant, such as the fire blight of pear and 

 apple twigs. 



Dwarfing or atrophy of the affected parts of diseased plants. 



Hypertrophy or swelling of the affected parts. 



Formation of entire new structures, example ergot. 



Mummification. This occurs with a considerable number of the 

 fruit rots. 



Change of position of affected part. Example, witches brooms pro- 

 duced by certain fungous parasites. 



Destruction of the affected organs, example, grain smuts. 



Excrescences and malformations, such as galls, cankers, witches 

 brooms, rosette, and punks or fruiting bodies of the large wood-rotting 

 fungi. 



Exudations, consisting of pitch, gum, or slime-flux. 



Rotting of fruits, leaves, or of stems in woody-stemmed plants. 



In the inspection of nursery stock for diseases, we may classify 

 diseases according to the part of the plant upon which they occur into 

 (1) Diseases of foliage, (2) of twigs, branches and stems, and (3) of the 

 roots. 



In general, the diseases of foliage are not serious, except upon seed- 

 lings or young nursery stock. These diseases are important, however, 

 with the herbaceous plants. The diseases of the twigs, branches and 

 stems are often very serious with the woody-stemmed plants. Ex- 

 amples of such diseases are: 



Killing of twigs on roses, etc., by Botrytis. 



Killing of stems of conifers and deciduous trees by Nectria ditissima 

 and A^. cinnabarina 



The chestnut bark disease, which is the most destructive disease of 

 large trees known at the present time. 



The various apple cankers 



The rose and raspberry stem cankers. 



KilHng of twigs of stone fruit trees by the gray rot (Monilia). 



The various pine-stem blister rusts. 



The well-known black knot of cherries. 



Our last group, the diseases of roots, are especially serious, not only 

 because they destroy the feeding organs of the plant, but because they 

 cause more or less serious soil infection, oftentimes lasting for several 

 years or longer. Examples of this class of diseases are the well-known 

 crown gall and hairy root of fruit trees, various kinds of root rots, and, 

 finally, but by no means least, root diseases caused by nematodes or eel 

 worms. The latter are especially serious, because soil once infected 



