572 WEED FLORA OF IOWA 



Buckhorn (Plantago lanceolata L.). 



The smooth, brownish, elongated seeds consist of epidermal cells 

 with a small cavity and thick walls ; the outer walls become mucil- 

 aginous on the addition of water. The underlying cells are thin, 

 blackish, elongated, followed by a brown pigment layer as in the 

 last species. The aleurone cells and remaining endosperm cells 

 are of about the same shape and size ; the walls are provided with 

 small pore canals. 



Bracted Plantain (Plantago aristata Mx.). 



The seeds of this are similar in structure to those of P. lance- 

 olata. The walls of the epidermal cells are mucilaginous. The 

 underlying parenchyma cells and the underlying pigment layer 

 are followed by the endosperm and embryo. The cells of the 

 nucellus are narrow, elongated, and thick-walled. The cells of 

 the embryo are isodiametric and are thin-walled. Several species of 

 the genus have been studied by Harz*. Numerous earlier papers 

 and references will be found in Pammel's article in Transactions 

 St. Louis Academy of Science, 9 :91. 



RUBIACEAE, MADDER FAMILY. 



Bedstraw (Galium aparine L.). 



The dry fruit of the common bedstraw is provided with hooked 

 prickles. The epidermal cells are somewhat elongated, brownish. 

 The trichomes consist of single hooked cells with pitted walls. The 

 underlying thin-walled parenchyma cells are elongated. Harz ob- 

 served mucilaginous cells in this portion of the pericarp. The 

 testa is very much reduced, consisting of several layers of thin- 

 walled cells with granular contents. The endosperm consists of 

 an aleurone layer, thick-walled cells followed by a thick-walled 

 irregular layer of cells with pore canals. Contents consist of pro- 

 tein grains. 



*Samenkunde 2 ; 983. 



