﻿OVULATE CONES. I I 5 



greater part at least, the median longitudinal section of the cone. And this, too, 

 would be a matter of some surprise did we not know how loath museum custodians 

 may be to the sectioning of such and such " handsome trunk," forgetting the great 

 labor involved and the necessity for using absolutely the best material first, within, 

 of course, safe methods of work. We have shown that much may be learned of 

 the structure of cones like the present from the study of surface features alone ; but 

 after all, almost any trunk will do for general "exhibition purposes," although a 

 single large and well-cut section from a finely conserved trunk may show more of 

 critically important detail than could be learned from the macroscopic examination 

 of a pyramid of such trunks as large as Cheops, however often repeated. The 

 dictum of petrographers, that, " Ein Gestein muss tinnier zuerst mikroskopisch 

 untersucht werden? is as true of silicified plants as of non-fossiliferous rocks. 



BRACTS. 



The ovulate cone was in life completely inclosed, not unlike an ear of corn, in 

 a heavy husk of imbricating hairy bracts, several, or in places many layers in thick- 

 ness. These are borne more or less closely in spiral order on the lateral surface of 

 the peduncle throughout the greater portion of its length beneath the discophorous 

 shoulder just described. Although the summits of the bracts are usually broken 

 away so as to expose the seeds at the apex of the fruit, there are various prettily 

 preserved examples of fruits in which the inclosing husk is nearly complete. Such 

 a cone of Cycadeoidea Paynei is shown on plate xxiv, photograph 6. The basal 

 bracts plainly lack but little of the length of the upper ones next the seed cone, and 

 the supposed relative length is shown in the partly diagrammatic figure 56. The 

 bract bases have usually nearly the same shape in transverse section as the leaf 

 bases, but are often much expanded and heavy toward the tip, though varying 

 greatly in this respect in different cones. They are quite uniformly thickset all 

 over their surfaces by long hairs or ramentum, of about the same structure as that 

 borne by the leaf bases, but mostly smaller. (See photograph 4, plate xxxviii, 

 showing the transverse section of the bract of a cone of Cycadeoidea Marshiana.) 



It is said that stomata (149) have been found on the bracts of Bennettites Gib- 

 sonianus, but none have been detected in the specimens before us, the epidermis 

 not being usually well preserved. The ground tissue of the bract bases is seen in 

 many sections to consist in much-lignified cells, elliptical to elongate, several times 

 as long as their diameter, and everywhere exhibiting regularly disposed transverse 

 markings. The length of these cells rapidly increases, however, till near the bract 

 tip, where shortening again occurs, the transverse marking persisting throughout. 

 Also along the inner face of the bracts — that is, next to the fruit — the cells are 

 very heavy walled, less distinctly striate, much smaller, more elongate, fibrous and 

 bast-like. The amount of this dense upper zone of the lignified mesophyll may 

 vary considerably in different trunks. In certain cycads, as, for instance, Yale cycad 

 272, as shown in figure 60, A-c, the bracts are very large and the lower zone of 

 striate mesophyll of the tips much rounder celled than usual. Distributed through 

 the lower striated mesophyll are various gum ducts (cf. fig. 60, B, c). In the cen- 

 tral part of the bract beneath the dense upper mesophyll, and disposed on a plane 



