xxxvi] 



CYCADEOIDEA 



415 



Cycadeoidea micromyela Moriere. 



This Liassic species from Normandy has been fully investigated 

 by Lignier 1 ; originally referred to the Conifers, it was afterwards 

 described by Moriere 2 as Cycadeoidea micromyela. As regards 

 external features the stem is of the usual Cycadeoidea type: 

 Saporta 3 assigned it to the genus Platylepis. The secondary 

 xylem consists of tracheids with bordered pits on the radial walls 

 arranged as single contiguous rows, resembling scalariform pitting, 

 or as 1 2 rows of separate circular pits (fig. 538, A), a type 



FIG. 538. Cycadeoidea micromyela. A, tracheids from the stele. B, course of 

 the vascular bundles at the base of a leaf. C, section of a leaf-trace entering 

 the stele; ra, I, median and lateral lobes of the trace. (After Lignier.) 



different from that of the great majority of Mesozoic species. The 

 uniseriate medullary rays are 7 20 cells deep, a character recalling 

 the compact wood of Indian Williamsonia stems. Ramental 

 scales are for the most part replaced by long unicellular hairs 

 like those of Williamsonia scotica and some Indian stems. Lignier 

 states that true ramenta occur on the young leaves and in older 

 fronds become transformed by separation of the cells into long 

 tubes. Each leaf-trace arises as a single bundle dividing into 

 three as it leaves the stele and eventually splits up into several 

 collateral bundles (fig. 538, B, C). The stele is elliptical. No 



1 Lignier (01). 



3 Saporta (75) A. PI. L. 



Moriere (69). 



