Evans: Notes on genus Herberta 



201 



The bands of thickening just described soon become united by 

 median bands laid down on the free walls (Text fig. 12). These 

 leave a series of thin places on each side, which show at first 

 angular outlines. Almost simultaneously the bands on the vertical 

 walls increase in thickness and become connected by deposits laid 

 down between them, the result being that these walls acquire a 



Figs. 11-13. Herberta juniperina (Sw.) Trevis. 



II. Very young cell from the basal vitta of a leaf, surface view, X 1,000. 12. 

 Somewhat older cell from same vitta, surface view, X 1,000. 13. Still older cell 

 from same vitta, optical section, X 600. The figures were all drawn from speci- 

 mens collected by L. M. Underwood along the trail from Cinchona to Morce's Gap, 

 Jamaica, 280. 



continuous layer of thickening except for an occasional pit. At 

 first the original bands are thickened more conspicuously than the 

 intermediate regions and the vertical walls appear distinctly 

 scalloped when examined in optical section (Text fig. 13). But 

 the conditions just described are temporary. The thin places in 

 the free walls are gradually filled up by deposits of thickening, 

 becoming rounded as they diminish in size, and the depressions 

 between the scallops along the vertical walls become obliterated 



