54 BOTANICAL. GAZETTE .- [JANUARY 
phyll that forms mucilage ducts, we think is sporogenous from analogy with 
Torreya and Taxus; but as to the mucilage ducts in the leaves we have no 
evidence that the tissue is sporogenous. Can we say that the ducts in the 
leaves, though they look like abortive sporangia, are not abortive sporangia, 
while the ducts in the hump having the same appearance are really abortive 
sporangia? On the other hand, does the presumption that the ducts in the 
leaves are not abortive sporangia forbid ss ed the view that the ducts in 
the hump are abortive sporangia ? 
It seems reasonable to conclude, if the resin cavity of Torreya originates 
in abortive sporangia, that the mucilage ducts of Ginkgo also owe their origin 
to abortive sporangia. 
Summary 
1. The development of the strobilus proceeds from the bottom toward 
the top, the oldest sporophylls being at the base. 
. The development of the functioning microsporangium is probably 
like that of the cycads. 
3. The development of the mucilage ducts in the hump of the micro- 
ae is in general like that of sporogenous tissue. 
his origin of the mucilage ducts ‘in the hump may indicate that the 
Eos of Ginkgo have come from a peltate type like the micro- 
sporophylls of Taxus. 
I wish to acknowledge my indebtedness to Professor CHARLES J. 
CHAMBERLAIN, by whose suggestion and under whose direction the work 
was done.—ANNA M. Starr, The University of Chicago. 
EXPLANATION OF PLATE VII 
Fic. 1.—Longitudinal section of young strobilus, with sporophylls beginning 
to be evident; August 7. X20 
Fic. 2.—Longitudinal section of older strobilus, with mucilage ducts (4) and 
sporogenous tissue (s) starting at the base; July 29. X20. 
Fic. 3.—Longitudinal section of strobilus older than fig. 2, showing develop- 
ment proceeding toward the top; August 7. X20. 
1G. 4.—Longitudinal section of strobilus with mucilage ducts in all the 
sporophylls and the sporangia in the mother cell stage; September 2. X2 
Fic. 5.—Longitudinal section of young sporophyll, showing four cells that 
have ep: come from a single archesporial cell. 485. 
6.—Longitudinal section of the hump of a young sporophyll showing 4 
byodermal plate of four cells (h) strongly differentiated. 485. 
Fic. 7.—Longitudinal section of the same region of another sporophyll with 
three hypodermal cells (c) that have divided periclinally. «485. ae 
Fic. 8.—Longitudinal section of the same region of an older sporophyll a 
