3i8 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
Heteroecism of apple and wheat rust and hibernation of many fruit-rot 
fungi in cankers or mummied fruits, which in the Hght bf science are simple, 
easily comprehended facts, could without science have had but little more 
than the force of superstitions. The investigations which have given 
greatest value to seed steeps have been those that showed the part played 
by seedling and floral infection. Recommendations of general sanitation 
would be largely without force were it not that the underlying reasons were 
made obvious by scientific explanation. Of all the categories mentioned, 
perhaps the least dependent upon science and the most empirical is that 
relative to disease resistance, since some of our most valuable resistant 
varieties have been given to us by farmers, while many of the most sus- 
ceptible have been eliminated naturally. During recent years, however, 
knowledge of Mendelism and of biologic specialization has added a very 
important, truly scientific aspect to this somewhat empirical subject. 
Many crops are of such small acreage value that expensive methods 
of disease prevention permissible with more valuable crops are precluded. 
In such cases, modification of practice, as change of time of seeding, of crop 
rotation, of kind of fertilization, of degree of drainage, of age of seed, of 
depth of plowing, of proper relation of direction of rows to wind and light, 
has in many cases proved serviceable. The suggestion of such modifications 
depends upon most intimate knowledge of both crop and parasite, and full 
life-history studies of the ecology of the organisms are needed. It is obvious 
that for the establishment of proper quarantine restrictions the taxonomy 
and morphology of the causal organisms must be known. 
It is both impossible and unnecessary to assign any money values to 
the protection that has been given to American crop plants under the 
various categories mentioned. A few cases illustrative of efficiency may, 
however, be mentioned. Cereal seed steeps at a cost of less than three 
cents an acre effect practically complete elimination of certain smuts. Thus 
the saving of oats in one state with full utilization of this knowledge would 
be about 7,000,000 bushels. One spraying for peach curl is stated to prevent 
98 percent of the injury with a net profit of more than $400 an acre. In- 
numerable other examples over the whole range of crop production could 
be adduced. Perhaps the most striking cases of value of our science occur 
in connection with quarantine restriction and early extermination of an 
invading disease. Coffee rust reached Porto Rico in 1902 on stock brought 
to Porto Rico by a Dutch battleship from the East Indies. It was early 
recognized by the experts of the Agricultural Experiment Station at Maya- 
guez, and, though a foothold had been gained, the disease was exterminated. 
So complete was the elimination that not even a herbarium specimen of 
the rust can now be found in Porto Rico. If you will visualize the coffee 
plantations of America paralyzed by this devastating disease, you will 
give due thanks over your morning coffee to the efficiency of the Porto 
Rican Station's activity. Another notable eradication was that of the 
