EXPLANATION OF THE ILLUSTRATIONS 
Psaronius sp. nov. Heliotype reproductions of 
photographs of nitrocellulose peels from a silici- 
fied stem. Figure at top shows the stele of a cor- 
tical root with some secondary activity. Middle 
figure shows a typical root with well preserved 
cell-walls. Lower figure shows sclerenchymatous 
tissue between roots. Magnified 44 times. Carbon- 
iferous: Illinois. 
[72] 
