508 WEED FLORA OF IOWA 



portions of the glumes is this coat evident. It has no diagnostic 

 importance. 3. The Inner Epidermis is composed of elongated cells 

 with straight walls. 



Palet of Staminate Flower. Within the glume of the staminate 

 flower is the palet, a hyaline scale only 1 mm. or less long with 

 a notch at the end. In general structure, it is much the same 

 as the other thin envelopes, but the cell walls are thinner. 

 1. Outer Epidermis. The narrow, elongated cells are wavy in out- 

 line, but pits are lacking or are indistinct. Isodiametric cells are 

 thin-walled; jointed hairs also occur. 2. Inner Epidermis. Except 

 at the base, where traces of mesophyl are sometimes evident, the 

 inner epidermis immediately underlies the outer epidermis. 



Glumes and Palet of Perfect Flower. Both the glume and the 

 palet of the fertile flower closely envelop the grain at maturity, 

 the former being strongly convex, the latter flat except on the 

 edges, which clasp about the caryopsis. At the time of flowering 

 these envelopes are thin and of a green color, but at maturity they 

 are coriaceous, silicified and of a brown or mottled color. Under 

 the lens, numerous transverse wrinkles are evident on the glume 

 and on the middle or flat portion of the palet, the lateral portions 

 of the latter which clasp the caryopsis being smooth and shining. 



1. Outer Epidermis. Throughout the glume and on the middle 

 portion of the palet, the cells are isodiametric or moderately elon- 

 gated and are arranged not only in longitudinal rows but also in 

 irregular transverse rows, the wrinkles being formed by the out- 

 bending of the cells at the end walls and the inward bending 

 half way between. At the time of flowering, it may be seen that 

 at the outer surface the end walls are sinuous and the side walls 

 are compoundly sinuous, but farther inward the end walls are 

 nearly straight and the side walls are simply, not compoundly 

 sinuous. At the end of each cell nearest the apex of the envelope, 

 a cuticular wart bearing a group of pits is usually evident, par- 

 ticularly on the palet. About these warts the adjoining end walls 

 are more or less curved and the side walls are not so deeply sinuous. 

 At maturity the cell cavity beneath the wart is conspicuous (on 

 the palet nearly circular), but at the other end of the cell is nar- 

 row or not evident at all owing to the encroachment of the strongly 

 thickened walls. The cell contents during the early stages of devel- 

 opment are colorless, but later on usually become dark brown. The 

 epidermal cells on the lateral or smooth portions of the palet which 



