PRODUCTION OF TULIP BULBS. 37 



writer. In certain classes of infestation, wherein scattering leaves 

 through the planting are ''fired/' it is advisable to go through and 

 clip with shears the diseased portions and carry them out of the field. 



Weeds allowed to grow to such an extent that good aeration is want- 

 ing contribute to the development of the fungus. Some fire has oc- 

 curred in these experiments even on virgin soil when tulips have been 

 left in for two years, although properly handled stocks close by were so 

 clean that no fire could be detected. 



To sum up, clean culture, safe rotation, sanitation in matters 

 relating to the residues of the crop, annual lifting, care that the 

 planting stock be not bruised, or allowed to become moldy or to be 

 skinned in the bulb house are the preventive measures which will 

 render diseases of the tulip negligible. 



We may possibly consider as an exception to the above statements 

 the mosaic disease of tulips known as "breaking." Investigations 

 of this disease are now in progress, and it will be well to refrain from 

 positive statements on the subject until authoritative information is 

 obtained. A provisional discussion of this subject, however, will be 

 of value in this place, giving the results of the observations and opin- 

 ions of the writer and his horticultural associates. 



The "broken" tulips are sold as a distinct race by the florist. 

 They are listed as Rembrandts when derived from the Darwin 

 section (PL XVI, Fig. 2, and PI. XVII) and as "broken" tulips in 

 other sections of the tulip lists. They are distinguished by the 

 peculiar variegated or mosaic patterns of the floral coloration. These 

 same patterns extend into the leaves and other portions of the plants, 

 where the contrast of coloration, however, is less spectacular than in 

 the flower, because the breaking in the leaves consists in simply an 

 unequal distribution of the green coloring matter which results in a 

 delicate and often only indistinct pattern of varying densities of 

 green. In the flowers, however, especially when the ground color or 

 the color of the tissues between the epidermal layer is yellow and 

 that of the epidermis some brilliant shade, the pattern becomes 

 striking and often very beautiful. There is an exact counterpart of 

 this in the flower of the ornamental tobacco affected with the mosaic 

 disease, which has been extensively studied by Allard and others. 



The effect of the disease on tulips is precisely similar to the effect 

 of the mosaic on tobacco. There is a decided dwarfing of the plant, 

 a reduction of its powers of reproduction, and a general weakening of 

 its constitution. The "broken" tulips, therefore, are less satisfac- 

 tory to grow, especially if one is producing bulbs for sale, than the 

 self-colored forms. In short, the mosaic or broken plant is weak and 

 requires greater care and effort in the production of marketable stock 

 from it. The breaking in tulips is again analogous to mosaic in that 

 seedling stocks of broken strains are free from the disease. 



