﻿I IO 



REPRODUCTIVE STRUCTURES. 



and more peripheral insertion both sporophylls and interpolated scales decrease in 

 length and assume a gracefully increasing outward curve, thus producing a more or 

 less egg-shaped cone. Near the base of the fruit the surface is seen to be composed 

 of the expanded tips of the abortive sporophylls only, and, further up on the sides 



and summit, of rosettes of expanded 

 sporophyll tips grouped about the 

 ends of the long micropylar tubes of 

 the seeds, which are hence layered 

 in a continuous pericarp. The sur- 

 face of the fruit, wherever con- 

 served, thus completely displays the 

 arrangement of both kinds of spo- 

 rophylls, as seen not only in the 

 present but in other species and 

 shown in figures 55 and 57, and in 

 plates xxiii and xlvii. But more 

 often, as the result of erosion and 

 the breaking away of the tips of the 

 bracts, the layer of seeds is exposed 

 directly to view, those at the sum- 

 mit standing vertically to the sur- 

 face of the fruit and the lateral ones 

 nearly so, or at a slightly increasing 

 angle, these features being espe- 

 cially clear in several of the strobili 

 photographed in longitudinal thin 

 section (plate xxi). All of these 

 details, including the number and 

 arrangement of the bract husks, 

 may be determined by macroscopic 

 study unaided by a single thin 

 section. The description of the 

 structure of the ovulate cone, as 

 seen in thin sections, now follows. 

 In transverse thin sections cut 

 well beneath the summit of a fruit 

 two closely packed peripheral rows 

 of obliquely-cut seeds are usually to 

 be seen, as in plate xxv, photo- 

 graph 4, while interior to these is 

 the mass of interlocking intersemi- 

 nal scales and seed pedicels. In 

 passing from the center of such a 

 section to the peripheral row or 

 rows of seeds the pedicels and 





Fig. 56. — Ovulate strobilus o( Cycadeoidea. A drawing o( radial 

 longitudinal section 391 (T. 393), with partially restored bract 

 tips. (Compare with photograph 3, Plate XXIV.) 



The arrow indicates direction vertical to the trunk, the section passing through 

 the exact median and vertical longitudinal plane of [he axis ot fructification. 

 m. x, p. and c, respectively, the medulla, xylem, phloem, and cortex of 

 trunk as cut in radial-longitudinal section ; a, insertion of armor on cortex, 

 I , old leaf bases; d, insertion of dehiscent hypogynous disk ; s, erect seed 

 borne at summit of seed pedicel inserted on convex receptacle ; b, hair-cov- 

 ered bract. 



