94 THE PRACTICAL GARDEN -BOOK 



handle or any hardwood stick. When broad holes are 

 wanted, the triangular iron Dibber (sold by dealers) is ex- 

 cellent. It is particularly useful in hard soils. 



Dicentra includes the Bleeding Heart ; also 

 the native little Dutchman's Breeches and Squirrel Corn, 

 and a few other species. All are hardy perennials of 

 the easiest culture, blooming in spring. In common with 

 all perennial herbs, they are benefited by a winter mulch of 

 leaves or litter. Propagated by dividing the clumps. 



Dictamnus. FRAXINELLA or GAS PLANT. An 



old border plant (perennial herb) with white or pale red 

 flowers. The leaves of the plant emit a strong odor when 

 rubbed, likened to that of the lemon verbena. It has been 

 advertised as the Gas Plant from the fact that the plant 

 exudes an oily matter that may be ignited, especially in 

 warm, dry weather. Propagated by seeds, which should be 

 sown as soon as ripe. The plant blooms the third year, 

 and improves with age. Set plants 3 feet apart. Height 2 

 to 3 feet. 



Dill. An annual aromatic herb that will seed 

 itself if seeds are left to ripen, and an abundance of plants 

 may always be had. The culture is of the easiest. The 

 seeds are often used to flavor pickles. 



Diseases. Diseases of plants may be caused 

 by some physiological disturbance to the plant system, or by 

 the incursions of some parasitic organism, as insects or fungi. 

 The work of insects, however, is ordinarily not classed with 

 plant Diseases (see Insects). Of Diseases which are caused 

 by plant parasites or by physiological disturbances, there 

 are two general groups : 



(1) Parasitic fungous Diseases, such as the apple-scab, 

 black-rot and mildew of the grape, leaf-blight of the plum 

 and pear, black -knot, and the like. These Diseases are 

 characterized by definite spots, discolorations or excres- 

 cences, which are more or less scattered over the surface of 



