﻿OVULATE CONES. 



IO9 



GENERAL FEATURES. 



The ovulate cone is a laterally borne branch which arises from between the old 

 leaf bases or else from their axils in part, at any point between the base of the trunk 

 and the youngest series of leaves. The time and order of appearance will be con- 

 sidered later. Each of these specialized branches consists in an egg-shaped apical 

 cone, borne on a short peduncle and completely incased by a series of numerous 

 imbricating hair-covered bracts, as clearly shown in the drawing of a longitudinal 

 section (fig. 56). The bracts arise in spiral order from all of the lateral surface of 

 the peduncle, and close well in over the apex of the fruit. In trunk 393 the armor is 

 4.5 cm. in thickness and the cortex 1.3 cm. in the middle portions of the trunk. The 

 peduncles are usually 2 cm. in length by 1.5 cm. in thickness, and the length of 

 the approximately full-sized cones is from 4 to 4.5 cm., whence the larger forms 

 protrude a centimeter or two 

 beyond the armor. The greatest 

 strobilar diameter, which is 

 somewhat distal, is from 2 to 

 2.5 cm., exclusive of the cover- 

 ing of bracts, which is from 2 

 to 3 mm. in thickness. 



Before passing on to the 

 study of the microscopic struct- 

 ure of the strobili it will be of no 

 little interest to see what may 

 be learned from such fruits 

 without the aid of thin sections, 

 since the paleobotanist must so 

 often depend on casts and im- 

 pressions alone. And, indeed, 

 from an examination and com- 

 parison of superficial features 

 only, as seen in a considerable 



number of these ovulate fruits presenting the various stages of erosion and fracture 

 to be met with in the large cycad collections now brought together, it is possible 

 to determine their essential structures without thin sections. The bract-bearing 

 peduncle, as may be seen in the case of numerous dehiscent fruits and fractured 

 surfaces, terminates in a fleshy expanded and slightly convex receptacle or "pareu 

 chymatous cushion," as Carruthers called it, strongly reminding one of that seen 

 in the Composite. Upon this receptacle, usually of much lighter silica, is inserted 

 the compact, dark-colored, brush-like mass of interlocking, slender, and abortive 

 sporophylls, now and then split open lengthwise, as in the original type of Beunet- 

 tites Morierei {cf. plate xlvii) and in many Black Hills specimens. Each of the 

 fertile sporophylls bears a single apical and erect seed, which terminates in a long 

 micropylar tube. Each abortive sporophyll ends in an expanded tip. The centrally 

 inserted sporophylls are longest, and rise quite directly ; but in rising from the more 



Fig. 55. — Cycadeoidea sp. (T. 750) . Surface sculpturing of young ovulate 

 cone, 2.5 cm. in diameter. The ends of the micropylar tubes clearly 

 appear between the heavy polygonal ends of the interseminal scales. 

 Enlarged about ten times. From a photograph. (Cf. figure 29.) 



