1908] COULTER—GNETUM GNEMON 47 
basipetal succession. The inner one extends above to form the 
elongated micropylar tube, and at the maturity of the seed completely 
invests the nucellus (at this time replaced by the endosperm) as a 
papery layer. The outer integument becomes differentiated into 
an outer fleshy layer (white in the figure) and an inner stony layer 
(black in the figure), the latter completely investing the seed, the 
former being chiefly developed in the region of the nucellar beak. 
Two sets of vascular strands are present, the outer set traversing the 
fleshy layer of the outer integument, the inner set traversing the 
Inner integument. 
In Cycadophytes, Ginkgoales, and Coniferales, a single integu- 
ment becomes differentiated into a testa of three layers: outer fleshy, 
stony, and inner fleshy. In Gnetum the same three layers are 
Present, but the inner fleshy one has become differentiated in onto- 
geny as a separate integument. In all cases, this innermost layer 
finally forms a papery lining of the stony layer. Among the Pinaceae 
the outer fleshy layer is present in the integument, but it does not 
develop into the extensive pulpy investment that characterizes the 
Cycadales, Ginkgoales, and Taxaceae, a fact which is probably 
associated with the close investment of the seeds by the scales. 
The variation in the distribution of the vascular strands among 
these layers is interesting. Among the more primitive Cycado- 
filicales and Cordaitales, in which the nucellus is relatively free 
from the integument, the outer set of strands traverses the outer 
fleshy layer and the inner traverses the peripheral tissue of the nucellus. 
In other Cycadofilicales and Cordaitales, however, and in Cycadales 
which the nucellus and integument are free only in the region of 
the nucellar beak, the inner set of vascular strands traverses the 
aner fleshy layer of the integument; and this is the condition in 
Gnetum, except that this layer has become differentiated as an inner 
integument. In Ginkgoales the outer set of strands (belonging to 
the — fleshy layer) is suppressed; in Taxaceae the inner set 
(belonging to the inner fleshy layer) is suppressed; and in Pinaceae 
th are suppressed, 5 
MALE GAMETOPHYTE 
It was a disappointment that the development of the male gameto- 
phyte was hot secured, for it is only known among Gnetales in Ephe- 
