﻿126 REPRODUCTIVE STRUCTURES. 



there is a filling of the oospore with a compact protocorm tissue like that here 

 observed to quite fill the entire nucellus. From this the embryo arises and then 

 encroaches upon the endosperm by the growth of the whole mass (87^). In the 

 Cycadeoidese there is evidently present an analogous and possibly still simpler con- 

 dition. In any case, it is not surprising that the embryogeuy of these plants should 

 present features in common with Ginkgo. Doubtless the Cordaitales were also 

 characterized by this most primitive type of embryogeuy yet observed in the gym- 

 nosperms. 



It is only the fortunate exceptional section which tells the most when it comes 

 to the study in the fossil condition of such recondite characters as the present, and 

 it is of course necessary for most searching comparison to have at hand all the facts 

 displayed by all the specimens. Less may not ultimately suffice. I may hence 

 only add that with the large amount of material so urgently awaiting further 

 investigation it is, from the meager facts already observed, not extravagant to hope 

 that completer study will reveal an outline of cycadeoidean embryogeny ; and that 

 if this hope be realized, the connected evidence will perchance prove to be the 

 most important single paleobotanical chapter in the story of plant evolution that 

 may be brought to light. 



CONE-BEARING HABITUS. 



[As seen in the three Cycadeoidea Wieiandi trunks, Xos. jgj, 7J, fj/, 



and in the C. McBridei trunk Xo. 7<''+j , 7J.) 



The fruit-bearing habit of cycad 393 (cf. plate xxi) and the other trunks of 

 the species to which it belongs is of the greatest interest. The lower half of this 

 trunk bears three well-preserved ovulate strobili and nine others partly preserved 

 or iu part broken away, or shed, or that have failed of complete preservation. The 

 upper half of the trunk bears eight fine strobili, and about twenty-six more such 

 have been broken away, together with their surrounding armor, being indicated only 

 by the basal portions of their peduncles. The total number of ovulate fruits borne 

 by the entire trunk is therefore seen to be nearly fifty, all these cones being in rela- 

 tively the same stage of growth. In addition to those enumerated there are doubt- 

 less several smaller axes so embedded in ramentum that they have been overlooked, 

 or that might not in any case ever have matured. The general stage of growth 

 throughout the series is, however, so nearly uniform that the forty-six larger fruits 

 distributed nearly equally over all the lateral surface of the trunk must be regarded 

 as belonging to the same season. Moreover, it appears that no earlier series of fruc- 

 tifications was borne by this plant, and it is quite unlikely that other fruits than such 

 as are included iu the series just enumerated would later have been produced had 

 fossilization not chanced to intervene. It would seem that, much like Coryplta 

 umbraculifera, the trunk never produced fruits until it reached a full maturity, and 

 that all its energy of fructification was then put forth in an effort that at most lasted 

 but a few seasons. How long it may afterward have continued its vegetative 

 growth is a matter for some speculation, but as the present species seldom formed 

 trunks more than 2 feet in height, and no series of old peduncles has been observed, 

 it is not likely that it survived active fructification more than a season or two at 

 the most. A fair estimate of the age of the trunk is about half that of a trunk of 



