﻿OVULATE CONES. I 23 



sections certain traces interior to the nucellus may represent a tapetum, and that in 

 various instances, notably in section 103, etc., a strongly developed megaspore 

 membrane is clearly indicated. Such a membrane lying interior to a tapetum has 

 been found quite universally present in the gymnosperms, evidently being a slowly 

 disappearing structure inherited from a pteridophytic ancestry, since it is of vesti- 

 gial appearance in forms like the Gnetales, more prominent in the primitive mem- 

 bers of the group like the cycads and Ginkgo, and most highly developed in the 

 seeds of the Cordaitalean complex (167a). As this membrane is also prominent in 

 the Paleozoic seed-bearing quasi-fern Lagenostoma (109), it may be assumed to have 

 characterized all of the Cycadofilices. Since a megaspore membrane was so 

 evidently present in the ancestral Cycadeoideae, it would not likely have become 

 wholly obsolete in any of the group by the Mesozoic. Its indubitable preservation 

 being atbest fortuitous, need not, however, be expected in all the genera; and per- 

 chance just as this recondite pteridophytic structure has waned in the Gnetales with 

 more suggestions of angiosperm contiguity than the conifers, so the assumption by 

 the Cycadeoidece of the angiospermous juxtaposition of floral organs may in some 

 forms be found to have been correlated with a similar spore-coat reduction. 



Integumentary structures and homologies in Benncttitcs Morierei and Cyca- 

 deoidea Wielandi. — The structure of the integument of the seed before us will be 

 seen to compare in the main with that of the already well-known Bennettites Gib- 

 sonianus and B. Morierei, but not within the limits of closely allied species, as I 

 formerly thought, unless, indeed, thickening of the apical layers of the testa took 

 place after the growth of the embryo.* The seed coat or integument of Bennettites 

 Morierei Sap. et Mar. is single-walled and consists, firstly, in an outer simple and 

 highly characteristic enveloping layer (b) strongly palisaded above ; and secondly, 

 in a more complex inner layer of soft tissues (V), made up of a single layer of cells 

 having the appearance of a palisaded parenchyma followed next to the nucellus by 

 a layer of rounded, thin-walled cells several to four or more cells thick above. But 

 outside the integument, as thus described, are certain tubular cells (/), which Lignier 

 considers to belong to the seed coat, although they may better be assigned to the 

 outer layer of the interseminal scales. The seed coat is, therefore, excluding these 

 tubular cells, primarily double layered, with the inner layer the more complex. 



The integument of C. II "ie landi Ward is also single- walled and two-layered, 

 but there are some striking differences from B. Morierei, making it very difficult to 

 homologize the layers in these two species with certainty. Both layers are much 

 thinner, making the comparison in each case with seeds containing embryos. The 

 outer or epidermal layer (c) (cf. figure 63), which lies next to the tubular cells of the 

 interseminal scales above, or the outer cortical and basal husk below, as the case 

 may be, is one cell thick, the cells varying from more or less cubical to seven or eight 



* Fortunately I have been able to give my own description with some small but otherwise very beau- 

 tiful and representative sections of the historically important Bennettites Morierei before me. The 

 duplicate sections were made by Professor Lignier, and loaned to Professor Ward, who brought them 

 from France. Later, with Professor Ward's permission, I effected an exchange with Professor Lignier of 

 sections from Black Hills material for these important sections of the type of Bennettites Morierei, which 

 are now in the collection of the Yale Museum. 



