570 WEED FLORA OF IOWA 



SCROPHULARIACEAE, FIGWORT FAMILY. 



Mullein (Verbascum thapsus L.). 



The minute, roughened seeds are irregular. The epidermal cells 

 are dark colored, longer than broad and thick-walled. The epider- 

 mal layer is followed by one or more layers of parenchyma cells, 

 more numerous in the micropilar region; an indistinct and com- 

 pressed layer with large intercellular spaces follows, these corre- 

 sponding to the irregularities on the surface, smaller intercellular 



Fig. 435. Microscopic structure of the seeds of the Figwort family (Scrophul- 



ariaceae) . 

 I Moth Mullein (.Verbascum blattaria). II. Common Mullein (Verbascum 



thapsus). 

 ep=epidermis. p=parenchyma. al=aleurone layer. en=endosperm. em=em- 



bryo. 

 (Drawings by L. H. Pammel and Charlotte M. King.) 



spaces occurring between the larger. The nucellus is compressed, 

 showing remnants of cell walls. The endosperm consists of an 

 outer aleurone layer, the walls with pore canals; this is followed 

 by cells of the same character. The cells of the embryo are 

 smaller. The testa of Verbascum blattaria in an undeveloped seed 

 consists of the epidermal cells with chlorophyll and the underlying 

 much larger cells also with chlorophyll. 



