666 



WEED FLORA OF IOWA 



pigment. The testa is thin, consisting of thin-walled parenchyma 

 cells with granular contents. 



VERBENACEAE, .VERVAIN FAMILY. 



Hoary Vervain (Verbena stricta Vent.). 



Epidermal cells thick- walled ; outer cells colorless. Underneath 

 this lie several layers of pigmented cells, slightly longer than broad. 

 This layer is followed by rather thick-walled, colorless cells, witii 

 small cell cavity; one or two rows toward the middle are thick- 

 walled and smaller. Next follow the cells of the embryo. 



FiQ. 432. Mlscroscoplo structure of seed and fruit of Vervain iVerbena atrlcta'). 



ep=epldermls, thlok-walled. p=parenchyma layer, pl^pigment layer of small 



parenchyma cells. The two inner layers of cells of the testa. 



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



LABIATAE, MINT FAMILY. 



Catnip {Nepeta cataria L.). 



The small dull brown seeds are finely roughened. The pericarp 

 consists of an epidermal layer with thin cuticle, on the addition 

 of water becoming mucilaginous. This layer is followed by under- 

 lying parenchyma cells, then the Malpighian cells with conspicuous 

 light line. The cells are colored yellowish brown ; underlying this. 



