216 
mother plant down to the seed produced by it. Therefore in every 
kernel of seed there is concealed the whole relation between the 
development of the plant and the total heat of the locality where it 
was produced. ‘Two seeds of the same species, one of which comes 
from a mother plant that has lived under the influence of an annual 
total heat of M, but the other of which comes from another mother 
plant that has lived under a total annual heat of N, possess powers of 
development, or a sensitiveness to equal temperature influences, that 
are inversely proportional to the sums M and N; or, in other words, 
the rate of development is equal to the sum of the effective tempera- 
tures divided by the normal values of the total annual sums for the 
mother plant. 
Applying this law to seeds that are artificially transported from 
their homes to other places having different climates as to tempera- 
iure we are enabled to predict approximately what their behavior 
will be. Thus Von Baer observed that cress seeds that had been — 
raised in St. Petersburg (lat. 60°) and transported to Matotschkin- 
Schar (lat. 73°) developed in July at only one-third the ‘ate that 
they did in St. Petersburg in the month of May. Now the annual 
sum of positive temperatures for St. Petersburg is 2,253° C., and 
the average temperature of the month of May in St. Petersburg is 
11.2°, while that of the month of July at Matotschkin-Schar is 44°. 
Therefore the rates of development per day of the same seed at these 
two places will be in the ratio of 11.2 to 4.4, or 2.6 to 1. Again, for 
cress seeds raised at Matotgchkin-Schar, where the annual total heat 
is 330° C., the rate of development will in general be 2253, or 6.8 
times more rapid than the development of seeds brought from St. 
Petersburg. Vice versa, seeds carried from Matotschkin-Schar to 
St. Petersburg the rate of development will be 6.8 times more rapid 
than for those that are native to the latter climate. 
Linsser was thus able to enunciate the first step in the rational ex- 
planation of a phenomenon with which agriculturists had long been 
familiar—viz, that the seeds raised in northern zones retain the 
power of rapid development, so that when sown in southern regions 
they grow more rapidly and ripen earlier and give a richer harvest 
than those that are sown in their native warm locality. Similarly, 
seeds of mountain plants, when carried by rivers into the warmer 
plains of the lowlands, develop plants whose blossoms antedate the 
spring blossoms of the plants native to the lowlands.” We may thus 
accept the general statement that plants or seeds transported to 
colder countries reach a given stage of vegetation later than the 
aA beautiful illustration of this law is found in the abnormal early flowering 
of seeds brought from the cold uplands and lodging on High Island, on the 
Potomac, about 5 miles above Washington, D. C. 
