CYCADEAE, MEDULLOSEAE. 97 



expansion. The outer boundary of the nucellus can be seen in the form 

 of a stout line, and this is surrounded by the testa which was formed from 

 the integument. The testa coheres below with the surrounding tissues, and 

 contains a layer of shortly prismatic palisade-cells with a stout membrane 

 and copious brown cell-contents. At the apex of the seed it runs out into 

 a long exostome, which at first broad and inclosing a conical nucellar 

 process probably surrounding the pollen-chamber, ultimately narrows into 

 a tube, and then after becoming a little broader terminates in the surface 

 of the cone. The behaviour of this integument is not represented by 

 Carruthers, and is only to be observed in single seeds which have been cut 

 through with more than usual success. The figure in the text had to 

 be obtained from several individuals. The same may be said of the 

 cell-contents. I have satisfied myself by searching examination of seeds 

 in the British Museum which I have myself prepared, that inside the 

 membrane which is all that remains of the nucellus there is a normally 

 disposed embryo with two fleshy cotyledons lying flat on one another. 

 The embryo so entirely fills the space as to preclude the presence of 

 any endosperm. Carruthers' l figure gives an indication of this embryo. 

 The sketch in Fig. 5 shows somewhat diagrammatically the radicle, the 

 vegetative point, the cotyledons, and their vascular leaf-traces which unite 

 to form the vascular axis of the hypocotyledonary member. Such de- 

 lineations as these it is true are seldom met with, for most seeds are not 

 sufficiently well preserved ; but we can very commonly observe in trans- 

 verse or oblique sections the division between the cotyledons as a transversal 

 fissure passing through the inner mass of the seed. 



The sketch here given of Bennettites, which I hope to make more 

 complete at some future time, is sufficient to show that its fructification 

 departs essentially from all that we are accustomed to find in the Cyca- 

 deae ; it is sharply and sufficiently characterised by its apparently axillary 

 origin, by the peculiar immersion of the seeds in the surface of the cone, 

 and by the absence of endosperm. It is possible that the seed-stalks may 

 prove to be carpophylls of a peculiar kind ; in that case we should be 

 obliged to separate the Bennettiteae altogether from the Cycadeae, and to 

 regard them as an intermediate group between Gymnosperms and Angio- 

 sperms. We should then have a typical case of that which Saporta and 

 Marion 2 call proangiospermy, though we could not perhaps assume a direct 

 derivation of Angiosperms from this plant, and though it may have belonged 

 to a line of development which never reached our era. However this may 

 be, we must at all events insist on the near connection of Bennettiteae with 

 true Cycadeae on the ground of the structure of the stem. The peculiar 



1 Carruthers (4), t. 59, f. 9. 2 Saporta et Marion (2). 



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