BULLETIN 
TORREY BOTANICAL CLUB. 
Vol. Xi] New York, November, 1886. [No. Il. 
The Pores of the Libriform Tissue. 
By EmILy L. GRreEGory, Ph. D. 
The objections against the imbibition theory of the passage 
of the sap through the cell walls, and the growing favor with 
which the opposite theory is regarded, namely: its passage 
throngh the cell lumina, have suggested a question in regard to 
some anatomical facts that have hitherto been disregarded. As 
the theory accounted for the upward movement of the water 
through the agency of the cell walls of the woody or libriform 
tissue of the stem, no special interest attached itself to the differ- 
ence in the form or frequency of the pores of this tissue. There- 
‘fore, while the anatomy of the woody tissue has been thoroughly 
studied and described by various authors, Sanio, Hartig and 
others, certain points of difference in the libriform tissue have 
received no mention from these authors, and as these facts appear 
to have a direct bearing on the theory of water movement 
through the cell lumina, a brief consideration of them may not be 
_wholly without interest. 
A few words of explanation are here necessary to show why 
a difference in function is inferred from this difference in the an- 
atomy of the pore. Assuming the passage of the sap through the 
lumina, it is plain that the different elements of the wood (holz- 
kérper) contribute in different degrees to this result; other things 
being equal, those being most efficacious whose lumina have the ® 
greatest diameter. Therefore the trachee take the first rankand __ 
are supposed to be channels through which the water is passed 
upward to the leaves, instead of being mere reservoirs of water. 
Assuming this of the trachez, it may be supposed that the thin- 
