1 3 ^ 
Notice of Book. 
from cell to cell, and if this be so there is no reason why the pores 
should not be formed after the sliding growth is completed. It is 
certain that vessels and other elements with sliding growth have 
corresponding pits. These pits must be developed when the mutual 
displacements are at an end, and it is quite likely that the per- 
foration of their closing membranes may take place at the same 
time. We must wait for further researches on the development of the 
protoplasmic strands in the cell-wall before this point can be deter- 
mined. It is of interest to note that, according to the researches of 
Fischer *, the sieve-tubes are connected by fine protoplasmic strands, 
not only with one another, but also with their companion cells; 
but that neither of them are connected with the cambiform cells. The 
latter, however, are in communication among themselves. It would 
be important to ascertain whether these differences have any relation 
to the sliding growth of the various elements on one another. 
It may be hoped that Dr. Krabbe’s work will lead to much im- 
portant investigation along the lines which he has indicated. 
D. H. S. 
1 Neue Beitrage z. Kenntniss d. Siebrohren, Berlin, Gesellschaft Wiss. 1886. 
