216 



mother plant down to the seed produced by it. Therefore in e\erv 

 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 conies from another mother 

 l^lant 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- 

 ture we are enabled to predict approximately what their behavior 

 will be. Thus Yon 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 rate that 

 they did in St. Petersburg in the month of May. iSTow 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 -1.4°. 

 Therefore the rates of development per dav 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 Matotschkin-Schar, where the annual total heat 

 is 330° C, the rate of development will in general be ^^, 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 



"A beautiful illustration of this law is found in the abnormal early iiowering 

 of seeds brought from the cold uplands and lodging on High Island, on the 

 Potomac, about 5 miles aliove Washington. I). C. 



