PASSAGE OF WATER FROM PLANT CELL. lO/ 



their pale lower surfaces uppermost, they attract attention to the 

 tree which would otherwise be easily overlooked in winter, as it 

 is rather small and not at all abundant.* 



Tuscaloosa is probably at present the most convenient point in 

 the eastern United States at which to study the boundary between 

 the Palaeozoic region and the coastal plain, for nearly everywhere 

 east of here the coastal plain is bordered by ancient crystalline 

 rocks (as at all the well-known fall-line cities from Columbus, 

 Ga., to Washington, D. C, and even Xew York), and west of 

 Alabama there happen to be very few important towns along the 

 fall-line. Here the relations between geology and flora are very 

 striking. ]\Iost of the species above mentioned, as well as several 

 others seen on the same day but not mentioned, are not known to 

 occur in the coastal plain at all, though at this point, if not else- 

 where, they approach within a very few miles of it. The reasons 

 for this are mostly too complex to be discussed here, but are all 

 originally dependent on geological history. While climatic fac- 

 tors may and do bring about profound differences in the floras of 

 dift'erent parts of the earth, such factors are rarely responsible for 

 abrupt changes in vegetation such as we see here. 



THE PASSAGE OF WATER FRO^I THE PLANT CELL 



DURIXG FREEZING. 



By K. M. Wiegand, 

 Cornell University. 



In a previous number of this journal f the writer has attempted 

 to outline the occurrence and structure of ice masses within plant 

 tissue. The present paper deals with the question of how the 

 water gets from the cell cavity into the intercellular spaces during 

 the process of ice formation, there to be converted into ice. In 

 regard to this point two general theories have been held, which 



* A little later in traveling over the state I was able to recognize this tree 

 from moving trains at many points where if the leaves had all been lying 

 face up I would not have noticed it at all. 



t Vol. 9, no. 2, Feb., 1906, p. 25. 



