82 BOTANY OF CROP PLANTS 



The awns or beards are brittle-like structures on lemmas or 

 glumes, usually on the former. They are commonly termi- 

 nal, as in wheat, or dorsal (attached to back of lemma), as 

 in oats. Zoebel and Mikosch, working with two-rowed and 

 six-rowed barleys, arrived at the conclusion that awns are 

 transpiring (water-losing) organs. They noted that bearded 

 barley spikelets transpired more than artificially beardless 

 ones of the same sort under similar conditions. They also 

 observed that, at the time of kernel development, transpira- 

 tion from the spikelet was most intense, probably corre- 

 sponding to the time of greatest movement of reserve ma- 

 terial to the kernel. 



Up to 1906, Hackel reports 67 species of cleistogamous 

 grasses. As compared with flowers that open, cleistogam- 

 ous ones generally have reduced lodicules, smaller anthers, 

 a shorter pistil, and less pollen. In a few cases {Panicum 

 clandestinum) for example, -claasmogamous spikelets and 

 cleistogamous spikelets may occur in the same inflorescence. 

 According to Koernicke, two-rowed erect-eared barley 

 {Hordeum distichon erectum) bears only cleistogamous 

 flowers. 



Pollination. — Wind is the chief agent in the dissemination 

 of grass pollen. In all grasses the pollen is light and dry, and 

 hence easily blown. Insects play a very unimportant part 

 in this process. 



Most grass flowers open to shed their pollen, that is show 

 chasmogamy. In some grasses, however, the glumes do not 

 spread apart, thus allowing the stamens and pistils to be- 

 come exposed. Flowers that do not open are said to show 

 deistogamy. 



Fruit. — In all grasses, the fruit is one-seeded, dry, and does 

 not spUt open at maturity to allow the seed to escape. The 

 pericarp (ovary wall) is firmly attached to the seed coat. 



