﻿BISPORANGIATE AXES. 



I6 5 



RESUME. 



The silicified pollen-bearing flowers of the Cycadeoidese at present known are 

 all bisporangiate, unexpanded, and borne laterally on the main stem as altered 

 branches or shoots, projecting but little, or not more than several centimeters, beyond 



the surrounding armor of leaf bases 

 and ramentum. The flower or stro- 

 bilns as thus borne on a short and 

 heavy peduncle consists in a termi- 

 nal ovulate cone surrounded by an 

 hypogynous stamiuate disk and an 

 outer series of enveloping bracts, fol- 

 lowed by the old leaf bases of the 

 armor. The ovulate cone is elon- 

 gate, and its ovules are young and 

 borne on very short pedicels, the 

 agreement in structure with young 

 forms of various other ovulate cones 

 being very close. The stamiuate 

 disk is formed by a series of from 

 ten (in C. Jenneyanct) to eighteen or 

 twenty (in C. dacotensis) once-pin- 

 nate fronds with a strong basal adna- 

 tion of their petioles continuing 

 nearly to the level of the summit of 

 the central cone; whence the stro- 

 bilus has the form of a campanulate 

 flower. Each frond bears about 

 twenty pinnules closely set with two 

 sub-laterally attached rows of dis- 

 Fig. 88.— Cycadeoidea. tichous and sessile syuangia, and is 



Restoration ol an unexpanded bisporangiate strobilus. with part o( the envel- . . ~*~*JCMnt\n-n 

 oping hairy bracts removed. E.ghteen folded fronds are shown as in Of partially CirClUliate pretoliatlOll 

 Cycadeoidea dacotensis. About natural size, or not nearly so large as , ^„„fl__. f - „\ K^incr rmrp ill- 

 various examples. (Compare with figures 70 and 71.) (OT preUOratlOllj, bdllg OllCe 111- 



flexed, so that the upper third of its length lies with the ventral surface of the rachis 

 appressed to the central cone, the fertile pinnules being folded back in pairs 

 between the ascending and descending limb of the rachis. And since the pinnules 

 follow in close order, all this intervening space is densely packed with synangia, 

 the sporangial loculi of which are often filled with pollen. 



The compact bud-like form and fairly mature stage of growth in a protected 

 position, as may be noted in passing, were very important factors in preservation. 

 Even had the large and feathery stamiuate fronds of the disks been silicified in an 

 uncurving or an expanded position instead of a closely folded one, they would 

 have been subject to crushing and breaking, with more or less comminution while 

 vet embedded; or they would have been broken away and destroyed during the 

 process of weathering out, as the tips of the bracts often are. 



