138 G. H. Widand — American Fossil Cycids. 



Fio. 1. 



Fig. 1. Bennettites Moriirei type (Sap. et Mar.), x 75. 

 Transverse section of seed stem traversing point of greatest constriction 

 exactly where expansion into the hilo-chalazal region begins (Camera lucida 

 drawing reduced from x 280). 



X, xylem or central tracheid region 

 surrounded by stem ground tissue ;• 

 P, small celled outer ground tissue ; 

 C, stained layer = "' assize colorie" ; 



imbricate to pleated layer = 

 " assize plissie "; 

 tubular cells of cortical region 

 forming exterior of seed stem, 

 and basal husk of seed ; 

 E, outer woody layer of the enveloping interseminal scales. 

 As connoted the layer E is the ligneous epidermis of the five to six inter- 

 seminal scales which completely enclose the seed-stem, being thus no true 

 part of the testa, though often splitting off with the seed, and sometimes 

 approximating a confluent growth. 



The elements of the testa here appear in their simplest form, the section 

 passing precisely through the transition region where the radio-symmetric 

 seed-stem handle passes over into the seed-base and testal structures. The 

 xylem (X) is exactly on the point of expanding to form the cup-shaped base 

 of scalariform tracheidal tissue supporting the nucellus, though still deeply 

 enclosed by the fundamental tissue of the seed stem. In the mass of the 

 latter, however, various resin cells characteristic of coniferous seed-base 

 tissue (Sequoia, etc.) begin to appear, and peripheral groups of small cells 

 basal to the inner flesh lie next to the conspicuous zone of resin filled cells 

 (C). The latter gives origin to the middle zone of the testa and is strictly 

 homologous with the gymnospermous "middle stone," though taking pre- 

 cisely the same mineral stain as the resinous cells scattered in the ground 

 tissue about X. The third concentric layer, A, also a single cell in thick- 

 ness, must be the continuation of the endodermis of the seed-stem bundle ; 

 it gives rise to the true outer flesh analogue, in this seed none other than the 

 so-called '"blow off" layer of the Carboniferous seed ferns. Finally the 

 rapidly thinning and fraying zone of large, stringy tubular cells ( T) is noted 

 as the well-conserved continuation of the cortical region of the seed stems, 

 which takes origin on the strobilar receptacle as a much thicker zone of small 

 cells. 

 (From a section cut by Professor Lignier.) 



