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 PL 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. 
