﻿Il8 REPRODUCTIVE STRUCTURES. 



produces with the pedicels an exquisite lace-like pattern. As the summits of the 

 interseminal scales are approached the chief change in the several tissue systems 

 is observed in the number, form, and distribution of the large, almost duct-like 

 sub-epidermal or cortical cells. These cells occur singly or sparingly in all the 

 lower peripheral portions of the scales, but increase markedly in number and 

 shorten toward the summit, the expanded portion of which is finally made up of 

 short to elongate and much-lignified cells with scalariform marking, groiiped more 

 or less radially to the few-celled central xylem strand, which may be traced, if the 

 section cuts through the true median longitudinal plane of the scale, quite to the 

 surface of the fruit. 



In longitudinal sections of fruits it is not always easy to detect the structures 

 of the interseminal scales, so much are the tissues of which they are composed like 

 those of the seed pedicels ; but since the position of the seed pedicels may be so 

 readily picked out, one may see, as very clearly shown in longitudinal section in 

 photographs i and 2, plate xxix, that the outer layer of the scales is always inserted 

 deeper on the receptacle than is that of the outer pedicel layer, a fact which might 

 perchance be construed as indicating each pedicel to be somewhat shoot-like. It is 

 not possible to pick out any short, distinctly parenchymatous cells surrounding the 

 central bundle. The characteristic part is the summit, with the central xylem 

 strand or bundle of the scale continuing into the tip and the more and more 

 strongly lignified cells of the cortex ranged radially to it with more or less regu- 

 larity. That the lateral walls of these latter cells are everywhere transversely striated 

 like those of the ground tissue of the receptacle and the mesophyll of the bracts is 

 a very important fact, going far in connection with the other structures to indicate 

 the homology of the bracts and the interseminal scales, and finally of the seed stems. 



A further fact indicating such homology is the presence of three or more 

 bundles disposed like those of the bracts in a horizontal plane in the basal scales 

 of Bennettites Morierei, very recently observed by Lignier. In the American 

 forms but a single bundle has been observed to traverse the scales, as just described, 

 although plural bundles will no doubt yet be found. The fact that the interseminal 

 scales exhibit dorsi-ventral as well as radial structure is most interesting, and denotes 

 not only homology to the bracts, but the probable presence in the Cycadeoidese of 

 transition forms of megasporophylls with dorsi-ventral rather than radial structure. 



THE SEED PEDICELS. 



The seed pedicels, as thickly borne by all the central surface of the receptacle, 

 are of cylindrical to subcylindrical form, their sides being closely appressed with the 

 surrounding interseminal scales en viasse. The length of the pedicels varies very 

 greatly, as noted in the description of the longitudinal section of the ovulate cone, 

 in the fruits of the same and different species, it usually being easy to trace the 

 outline of the pedicels throughout their entire length. The diameter of the pedicels 

 is nearly constant throughout, except just beneath the apically-borne seed, where 

 there is a distinct constriction, with compensating expansion of the interseminal 

 scales, above which the stem expands to form the seed base. The diameter of the 

 seeds is about a third greater than that of the stems. 



