THE AMERICAN BOTANIST. 35 



seem that such cold-loving plants as the saxifrages first ap- 

 peared near the poles when the world's first winter began. In 

 that winter of winters, the glacial period, the continental ice-" 

 sheets advancing southward drove the Arctic flora before 

 them. After other ages the ice began to melt from about the 

 Great Lakes, on the prairies of .the Mississippi Valley, and on 

 the Cordillera of the West. Step by step the glaciers with- 

 diew toward their northern home leaving behind them long 

 lines of moraine and glacial drift. Before the advancing 

 summer the Arctic plants retreated northward following close 

 after the glaciers. But not all returned, some found abiding 

 places in peat bogs and on cool northern hill sides. Some 

 were cut off and ascended mountain slopes, pushed higher and 

 higher by the advancing age of summer until they found their 

 present homes on lofty mountain peaks near the eternal snow. 

 San Anselino, Calif. 



EXPERIMENTS WITH SEEDS AND SEEDLINGS. 



By Willard N. Clute. 



POSSIBLY because the subject of botany usually begins 

 with seeds, or possibly because seeds lend themselves 

 readily to such a variety of experiments, we often find a dispro- 

 portionate amount of time given to seeds in botanical courses. 

 It is certainly true that after studying the structure of typical 

 seeds we should proceed to see what uses the parts have and 

 how ordinary conditions of heat, light, moisture and air act 

 upon them, but in doing so it is well to discriminate sharply 

 between those experiments which elucidate general physiolog- 

 ical principles and others which are concerned merely with 

 special structures and functions. In this latter category may 

 be placed the study of the "p^g" of squash and other cucurbit 

 seeds. In an exhaustive study of seeds the special way in 

 which the embryo of the squash gets free of the testa may be 

 studied and also the behavior of the cotyledons in the cocoanut 



