1908] COULTER— GN-ETUM GNEMON 47 



basipctal 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 

 in which the nucellus and integument are free only in the region of 

 the nucellar beak, the inner set of vascular strands traverses the 

 inner 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 outer fleshy layer) is suppressed; in Taxaceae the inner set 

 (belonging to the inner fleshy layer) is suppressed; and in Pinaceae 

 both are suppressed. 



MALE GAMETOPHYTE 



It was a disappointment that the development of the male gameto- 

 phyte was not secured, for it is only known among Gnetales in Ephe- 



