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CARNEGIE INSTITUTION OF WASHINGTON. 



Wieland, G. R., Yale University, New Haven, Connecticut. Associate in 

 palaeontology. (For previous reports see Year Books Nos. 2-4, 6-9, 

 11-20.) 



Preceding reports in the Year Book outline the main topics of fossil gymno- 

 sperm research still in hand. Emphasis rather than modification of these 

 outlines is recorded. The consistent aim during the past year has been, as 

 before, to study the major problems of gymnosperm evolution primarily from 

 structure and distribution, chiefly in the Mesozoic rocks. 



As no field work has been done during the past two years, accessions of 

 material have been limited to several casually reported finds. One in the Com- 

 anchean of Texas indicates a petrified cycadeoid extension of importance. 



Last winter Mr. Handel T. Martin, of the State University of Kansas at 

 Lawrence, forwarded a small armor fragment of a large petrified cycadeoid 

 from the Niobrara Chalk. This is very gratifying as being absolutely the only 

 known American occurrence between the Potomac, the Trinity beds, the 

 Dakota, and the Como, and the much later stems of the Upson shale and the 

 Belly River beds. Moreover, on sectioning, the specimen was found to add 

 one more species to the series of monocarpic cycadeoids. With this addition 

 in view, the general subject of monocarpy, as so remarkably exemplified by 

 the cycadeoids, requires a brief word here. 



MONOCARPY IN THE CYCADEOIDS. 



In the early work on the petrified cycadeoids it was observed that in some 

 instances large and evidently quite mature trunks bore few or no fruits, while 

 several monotypic species bore either a full complement of old or very elongate 

 peduncles or else the young undeveloped fruits in the axils of all old leaf- 

 bases. Such culminant fructification is commonly termed monocarpy. 



Some years later it was possible to add in demonstration the very remarkable 

 fossil plant, Cycadeoidea dartoni, bearing a full series of hundreds of mature 

 seed cones; while still later, an illustrated statement of the evidence for 

 monocarpy was given in the American Journal of Botany for April 1921. 

 But with one more species at hand from a marine horizon so well known for 

 its reptiles, fishes, and occasional dinosaurs, these instances of monocarpy seem 

 more directly significant. The monocarpic cycadeoids are the following: 



That is, the highly specialized columnar monocarpic cycadeoids stretched 

 across North America and later extended from the basal Cretaceous, past the 

 Benton, into the lands about the Niobrara Sea. Besides, the series early 

 reached cosmopolitan distribution (on the thirtieth parallel). 



Concisely put, the age of the several monocarpic species at fructification 

 can not be fixed from isolated types widely separated geographically. Only 



