PLATE 21 



A. — Longitudinal section of the tip of a young cob. X 300. 



B. — Longitudinal section of the rudiment or primordium of a spikelet just back of 

 the tip of a young cob: g, primordium of the lower empty glume. X 300. 



C. — Longitudinal section of the developing spikelet, showing the primordia of the 

 lower and upper empty glumes: g, lower empty glume; g^, upper empty glume. 



X 300- 



D. — Longitudinal section of the developing spikelet at a little later stage than C: 

 g, lower empty glume; g^, upper empty glume. X 300. 



