554 WEED FLORA OF IOWA 



Wild Liquorice (Glycyrrhiza lepidota (Nutt.) Pursh.). 



Testa and endosperm 490-500^ thick. Endosperm variable in 

 different parts of the seed, but usually well developed. 



Malpighian. — Cells 70-75^ long. Cuticle somewhat irregular; 

 the light colored cuticularized layer is followed by a narrow but 

 sharply marked zone, the light line ; cell cavity is large at the base, 

 gradually tapering upward. Pore-canals extend into wall beyond 

 the light line. Cells contain pigment and some plastic material. 



Osteosclerid. — The I-shaped cells are thick-walled, with small 

 projections somewhat similar to those shown for Ervum lens by 

 Mattirolo and Buscalioni. The intercellular space is elongated. 

 The cells attain their greatest development in the hilar region. 

 All of the cells carry some pigment and plastic material. 



Nutrient. — This layer is much compressed and thin-walled; cells 

 number from four to six rows. Pigment is most abundant in the 

 lower part of the layer. 



Endosperm. — Aleurone layer consists of nearly isodiametric 

 thick-walled cells. The mucilaginous reserve cellulose is variable 

 in quantity. Cell walls differentiated into primary, secondary and 

 tertiary. Internal part of the endosperm consists of thick- walled, 

 elongated cells. All of the cells contain protein grains. 



Embryo. — Cells of the outer row smaller than those within; ex- 

 terior walls thickened, those below more loosely arranged than the 

 epidermal ; more compact and with thicker walls than those of 

 Astragalus mexicanus. Cells contain fat and protein grains but 

 no starch. 



LINACEAE, FLAX FAMILY. 

 Common Flax (Linum usitatissimum L.). 



The shining, brownish seeds consist of an outer epidermal layer 

 of thick-walled cells; walls colorless and stratified; these become 

 mucilaginous on the addition of water. The cell cavity is very 

 small, the underlying layer consists of yellowish parenchyma cells. 

 The third, called the fiber layer by Winton, consists of sclerotic 

 parenchyma cells with pore-canals, the sclerotic parenchyma fol- 

 lowed by a layer of colorless cross-cells with thin walls. The 

 parenchyma cells of the pigment layer follow; these cells are 

 squarish, pigment yellowish brown. The endosperm follows the 



