332 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3 d Ser. 



the base and on the inner surface of the lower glume. This 

 outgrowth is at first on a level opposite the lodiculae, but 

 as the glume increases in length, it is carried upward some- 

 what (figs, i and 2). It becomes longer and broader and 

 forms the lamina of the mature lower glume, while the 

 original rudiment persists as the awn. 



The upper palet and the lodiculae arise apparently at the 

 same time and from the same rudiment (fig. 5). A cres- 

 cent-shaped ridge of tissue extends nearly around the pri- 

 mordium. This ridge does not form on the anterior aspect, 

 but from the ends the lodiculae develop, and from the 

 anterior face the upper palet. The upper palet grows as 

 the adjacent organs develop. When it can first be plainly 

 recognized it is composed of three layers of cells, and 

 later becomes thicker by periclinal divisions of the cells at 

 its base (figs. 5 and 6). The upper palet is the last of the 

 protective organs of the oat-flower to develop. 



The lodiculae appear as rounded shoulders jutting out 

 from the lateral surfaces of the primordium and mark the 

 ends of the rudiment that gives rise to the upper palet 

 (fig- 5)' The apex of the young flower grows up and 

 leaves the lodiculae in a lateral position below its tip. The 

 lodiculae are at first triangular with the broad base resting 

 against the surface of the primordium. They gradually 

 acquire the oblong shape characteristic of the mature 

 organs. 



The stamens of the wild oat arise as conical outgrowths 

 at equal distances apart around the periphery of the apex of 

 the flower. Figure 1 shows the relation of the anterior 

 stamen to the lower glume; and figure 7, which is taken 

 from a longitudinal section made a little to one side of the 

 center of the flower, shows one of the lateral stamens and 

 its relation to one of the lodiculae. The stamens develop 

 early, the filament appearing before the lamina of the lower 

 glume is well differentiated and while the carpel is still 

 small. It increases in length by cell-division in all parts 

 and is always relatively slender. The pollen is generally 

 shed before the stigmas of the flower have protruded from 

 the spreading glumes. 



