1897] MYELOPTERIS TOPEKENSIS 29 
Tannin sacs—In transverse section the tannin sacs are often 
barely distinguishable from the resin canals, by reason of their 
structural similarity. They occur abundantly in the cortex and 
throughout the fundamental tissue, and especially in close prox- 
imity to or within the limits of the vascular bundles. To me 
these appear to be the structures referred to by Mr. Seward in 
his description of Rachiopteris Williamsont, when he says, “there 
are smaller canals in the peripheral part of the phloem of each 
bundle.” In longitudinal section these sacs are seen to be of 
about the same diameter as in the transverse section, except in 
the cortex, where they assume the form of cylindrical cells about 
‘three or four times longer than broad. The contents are much 
lighter colored than those of the resin canals, and often present 
a well defined granular appearance. They readily yield the 
characteristic reactions for tannin. 
Resin canals.—Throughout the sub-cortical zone, scattered 
among the sclerenchyma cells and also central to each of the 
isolated strands, are rather broad canals of indefinite length. 
Throughout the fundamental tissue, particularly in the neighbor- 
hood of the vascular bundles, there are also numerous canals 
which differ but slightly in their structural aspects from the 
surrounding cells. In all cases, however, they are at once — 
recognizable by the rather dark red resinous mass which each 
contains. In longitudinal section the canals are of indefinite 
length. The contents are often septate. These structures 
appear to me to be comparable with the black, resinous masses" 
: a ee ro 
of variable size to be inek ate —— - the a — ; i : 
