16 



(6) Keep the plants clean of yellow, dead, or dying leaves, being 

 careful to destroy them after removing them from the plants, 



(7) Keep the plants free from insects and other animal pests. 



(8) Give careful attention to ventilating, heating, and shading the 

 houses or frames and to watering, cleaning, and cultivating the plants. 



(9) Renew the soil in the beds each season before setting in the yovmg 

 plants by removing from eight to twelve inches of the surface soil 

 and replacing it with that freshh^ prepared, 



(10) Set the young plants early in the spring in the beds where the}^ 

 are to remain during the season, so that they may get well estal^lished 

 before the hot. dry weather of summer makes its appearance. 



Careful attention given to the above directions for a number of 

 years will, it is believed, result in the production of a strain of plants 

 that are not only practicalh' disease resistant, but are also ideal as 

 regards regularity and symmetry of growth, length, and strength of 

 flower stems, and 3'ield, size, substance, and qualit}' of flowers pro- 

 duced. 



EXPLAXATIOX OF PLATES. 



Plate I. Healthy and diseased leaves of Marie Louise violet. (Natural size. ) Fig. 1, 

 healthy leaf. Fig. 2, naturally infected leaf. Figs. 3 and 4, artificially 

 infected leaves from the diseased plant shown in Plate lY. 

 II. Young plants of 3Iarie Louise violet from the cutting bed, showing spot 

 on the leaves. 



III. Fig. 1, healthy plant of ^larie Louise violet for comparison. Fig. 2, dis- 



eased plant (natural infection). 



IV. Fig. 1, healthy plant of Marie Louise violet (control). Fig. 2, diseased 



plant (artificial infection). 

 Y. Fig. 1, growth of the fungus in eleven days from a single spore <>n an 

 agar plate. Fig. 2, photomicrograph of mycelium and spores of Alter- 

 narki violee from violet leaves. Fig. 3, pure plate culture of Alfemaria 

 riola: 

 YI. Figs. 1 to 6, inclusive, show spores as they appear when brushed from a 

 diseased spot. Figs. 7 and 8, some of the same spores after nineteen 

 hours in distilled water in a van Tieghem cell. Fig. 9, a group of ger- 

 minating spores. The length of the germ tubes at the time of the first 

 examination is indicated by the dotted lines, and time marked; all 

 subsequent growth of these tubes occurred, and all unmarked tubes 

 developed, between the time marked and 2.10 p. m. Fig. 10, two con- 

 nected spores germinating at several points after l)eing about four hours 

 in distilled water. Fig. 11, germinating spore. Fig. 12, the same spore 

 twenty minutes later. Figs. 13 and 14, germinating spores. Figs. 15, 16, 

 and 17, spores produced on agar, showing manner of attachment to 

 mycelium and chain formation of spores. Fig. 18, pure culture of Alter- 

 naria rioliv on sterilized lima bean. The darker part of the culture is 

 thickly covered with spores; the white marginal portions are young grow- 

 ing mycelium. 

 VII. Fig. 1, healthy leaf <if California violet. Figs. 2 and 3, diseased leaves of 

 California violet, 



o 



