Further Notes on, Seed Structure. 



153 



there is, taking the lateral wall, a noteworthy parallel, and if 

 one had before him a complete series of both transverse and 

 longitudinal sections of the Abietineous species it is likely that 

 traces of apical ribbing would be found and that a composite 

 exceedingly like Cycadeoidea could be observed. 



And this line of study promises much interest; for the 

 Abietinean series was always regarded as a quite modern side 

 branch rather than an old gymnosperm stem terminal, until the 

 possession of really ancient structures was pointed out by 

 Hollick and Jeffrey.* These writers in their admirable study 

 of Cretaceous conifers show Pinus to be archaic and demon- 

 strate a new genus Prepinus of more primitive structure than 

 any other conifer living or extinct, while Jeffrey now insists 

 without reservation that the Abietinese are the oldest tribe of 

 conifers. f The decided resemblances in the seed wall structure 

 to Cycadeoidea lend further color to such views if any value 

 can be assigned to present-day features of gymnosperm seeds 

 in trying out questions of ancient relationships amongst great 

 groups of gymnosperms, using the name in any wide sense. 



Some closing remarks. — To anyone interested in the subject 

 of fossil seeds, it will not be necessary to say that even in the 

 case of seeds as well represented as are those of Cycadeoidea 

 finality in description cannot easily be reached. To secure 

 more exactly oriented sections, to illustrate these adequately 

 by both photomicrographs and drawings and gain an accurate 

 idea of the precise form and structure of the various species 

 of seeds is a work of time and perforce the task set for further 

 publication in connection with other features. But mean- 

 while, it may be stated that, regarding our view that a proem- 

 bryonic tissue occupying all of the nucellar cavity is present in 

 one species of Cycadeoidea, we still have no other explanation to 

 offer. Though it can be said that whatever the nature of 

 this tissue it seems to have been much given to bursting from 

 the nucellar sack. Scarcely better photomicrographs showing 

 the usual character and position of this tissue can be given than 

 that of the transverse section Plate XXX (9), where the slight 

 filmy tissue traversing irregularly the mass of rounded cells is 

 none else than the much wrinkled and collapsed nucellus, 

 though we were not at first prepared to believe that the 

 nucellus had so frequently collapsed, ruptured and floated 

 about in shreds amongst these cells as is now seen to be the 



* Hollick, Arthur, and Jeffrey, E. C. — Studies of Cretaceous Coniferous 

 Eemains from Kreischerville, New York. Mem. N. Y. Bot. Garden, vol. 

 Ill, 138 pp. with 29 plates. New York, 1909. 



f Jeffrey, E. C. — A new Prepinus from Martha's Vineyard. Proc. Boston 

 Soc. Nat. Hist., vol. 34, No. 10, pp. 333-338, pi. 33. Boston, 1910. 



