Wieland — American Fossil Cycads. 645 



Akt. XXXII. — A Study of some American Fossil Cycads, 

 Part VIII. 1 Notes on Young Floral Structures; by 

 G. R. Wieland. 



The developing fruits of the silicified cycadeoids 

 though variable in conservation, and in the smallest 

 forms merely casts with indistinct traces of cell struc- 

 ture, seldom fail to show points of interest. In some 

 instances the central cone fails of conservation, in others 

 the outer disk. But usually in even the smallest casts 

 the organs and tissue zones are delimited by color 

 gradation with varying forms of granulation; or the 

 tissues are traversed by sphenocrystic banding, often of 

 much beauty. Especially the palisaded zone of inter- 

 seminal scales and seed stems is from the early stages of 

 growth on, a sharply outlined part of the flower bud. In 

 fact young fertile organs but a fraction of a millimeter 

 in length and barely visible to the unaided eye are not 

 uncommon. An example is shown in American Fossil 

 Cycads by the writer, Vol. II, plate 35, photograph 4 

 (Carnegie Publ., No. 34). In most young fruits the 

 seeds early take on highly characteristic outlines, and 

 display the principal testal regions. Such seeds may not 

 show cell structure, but it is instructive to find the 

 forms but a few millimeters in length far sharper ribbed 

 than mature seeds. Disappearance of ancestral ribbing 

 is thus in evidence. 



The staminate organs, on the contrary, seldom appear 

 in the earlier stages as more than a cupule-like disk. 

 Even in larger forms the outlines of the individual 

 stamens may be indistinct ; but considering their paren- 

 chymatous, fugacious nature the staminate structures 

 are often so well silicified, as to repay scanning with 

 care. Although the ovulate outlines appear early, the 

 initial synangial growth is late. Young disks are for a 

 considerable time quite devoid of synangial traces. 



With the character of conservation thus briefly recalled, 

 it seems worth while to append a somewhat detailed 

 description of a young bisporangiate bud found during 

 the early part of the present year while studying a wedge 



1 Part VII of these studies appeared in this Journal for August' 1914 

 (vol. 38, p. 117). Eeferences to the earlier parts and supplementary 

 articles are there given. 



