MICROSCOPIC STRUCTURE OF WEED SEEDS 



665 



Fig. 431. Microscopic structure of some fruits of the Borage Family (.Boragin- 



aceae). 

 I. Stickseed (Lappula echincUa) part of fruit or bur. II. Stlckseed (Lap- 

 pula echinata). Enlarged view of epidermal cells showing irregularities in 

 cell wall and cavity. III. Wild Comfrey (Cynoglossum virginianum) . 

 ep=epidermal cells. n=nucellus. pl=pigment layer. en=endosperm. t=tri- 

 chomes. 



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



Stickseed {Lappula echinata Gilibert).. 



Tke fruits are rough and provided with hooked appendages, 

 the cells of the appendages are elongated, thick-walled, the walls 

 colorless; the cells of the epidermis toward the exterior are very 

 irregular with projecting rounded or sharp points, walls colorless. 

 The epidermal cells are elongated with central cell cavity and 

 prominent pore canals at right angles with the cell cavity, these 

 having the appearance of a series of cells one above the other. 

 The epidermal cells contain a brownish pigment, the underlying 

 parenchyma cells are thinner walled and also contain a brownish 



