l82 



MONOCOTYLEDONS 



the latter and the stem. Even in one and the same Grass- 

 plant both horizontal and ascending branches may occur 

 together. It is the 

 method of branch- 

 ing, together with 

 the direction of 

 growth of the 

 lateral shoots, 

 which determines 

 whether the par- 

 ticular Grass will 

 form a simple tuft, 

 a series of tufts, or 

 a mat-like layer. 

 Some Grasses 

 annual {e.g. 



are 



3 



Fig. 232.— A spikelet of Wheat. 



Wheat), others are perennial (e.g. Couch-Grass). 



Some annual Grasses, when sown in autumn, 



become biennial in that they rest during the 



winter and do not flower until 



the following spring. 

 Inflorescence. — The flowers 



are arranged in small spikes 



which are termed spikekts. 



A head of wheat (fig. 231), 



for instance, at first sight looks 



like a spike with two rows of . 



sessile flowers : whereas, in 



reality, it is a spike of spike- 

 lets. A spikelet (figs. 232, 



233) consists of a stem bear- 

 ing a few alternating bracts 



arranged in two rows, and 



a small number of sessile 



flowers with prophylls. The 



lowest two bracts (G, g) on 



the spikelet axis are termed 



glumes; one of them, the 



lower glume (G), is inserted 

 nearly opposite to, but at a slightly lower level than, the 

 other, which is the upper glume (g). These two glumes have 



of 



Fig. 233. — A scheme of 

 a spikelet of a Grass. 



