8 The Botanical Gazette. UJanuary, 
north before the advance of the glacial climate might be a 
forced during its advance to migrate southward to maintain 
their existence, and on the retreat of the same might climb up ~ 
spring blossomers might during the advance of glacial climate — 
maintain themselves zm sztu, by adapting themselves to the ~ 
more rigorous climate. On the retreat of the glacial condi- 
tions they might have so altered their habits as to be able to ~ 
maintain their existence only on mountain tops or in the dis- ~ 
tant north. Migration to these places would therefore set in. — 
It is probable that all these causes have operated in the pro- ~ 
duction of spring blossoming plants. It is impossible to tell 7 
duction is to be ascribed. It is sufficient for the present to — 
remember that nature has many means of accomplishing the g 
same result. ag 
Heidelberg, Germany. a 
The effect of mechanical movement upon the growth 
certain lower organisms. : 
H: L. ‘RUSSELL. 
: The effect of external agencies upon the growth of organ” 
isms has been thoroughly studied in several of its relations: 
Of these influences, the relation of temperature to growth, is 
perhaps the best understood. Other factors, such as the effe 
of light, of increased and diminished pressure, have also be 
made the subject of more or less careful study. 
f 
growth of cells in regard to size and form; (2) its influenc 
upon growth in regard toincrease in number. 
The method used in the experiments was as follows: 
Two 500¢. ¢. distilling flasks were half filled with nutri 
solutions, sterilized and then inoculated with a small quanti 
_ of the germ to be studied. After thoroughly distributing th 
