334 BOTANICAL GAZETTE [NOVEMBER 
field, where material may be abundant, it would be necessary to cut 
out the growing points of many plants to secure a few ovulate cones. 
And even then, judging from a slight examination of the ovule of 
Ginkgo, the integument of which also has two fleshy layers with a 
stony layer between them, we should be likely to find the integument 
arising as a single undifferentiated tissue. A study of the integument 
of Dioon after its various tissues have become somewhat differentiated 
also fails to give any definite evidence as to its single or double nature. 
_ [have been able to examine the integuments of several other cycads, 
but even where the differentiation between the layers is sharp, as in 
Zamia integrijolia, where the outer fleshy layer in both its cell-struc- 
ture and cell-contents is sharply marked off from the stony layer, and 
where the differentiation between the stony layer and the inner fleshy 
layer is also rather distinct, there is no satisfactory evidence that the 
integument has ever been anything but a single structure. In Cerato- 
zamia the layers are even less defined than in Dioon. 
Judging from the literature of the subject, especially from the work 
of Miss Stopes (16), who has made the most thorough investigation, 
no study of the integument of living cycads can yield conclusive evi- 
dence as to its single or double nature. However, a comparison of 
the cycad ovule with that of the fossil Lagenostoma lends much 
strong support to the theory that the cycad integument is a double 
structure. OLIVER and Scort'} suggest that the cupule of Lagenos- 
toma is equivalent to the outer fleshy layer of the cycad integument, 
while the canopy of a Lagenostoma may have become simplified into 
the stony layer of the cycad seed. Miss Stopes’ opinion is indicated 
by the title of her recent paper ‘‘On the double nature of the cycadean 
integument.”*© She believes that the plane of fusion between the 
two coats is either between the inner and outer portion of the stony 
layer or between the stony layer and the inner fleshy layer. The outer 
fleshy layer and the outer portion of the stony layer she believes 
to be too intimately connected to be separated morphologically. 
The structure of the Dioon integument, as it appears in sections, 
would seem to indicate that the plane of union has been between the 
inner and outer layers of the stone (fig. 11, et, i). The integument 
of Ceratozamia would bear a similar interpretation; but in Zamia 
integrijolia the outer fleshy layer is so sharply marked off from the 
