436 BRITISH FLOWERING PLANTS chap. 



good illustration of plants which are protected by barbs 

 at the edges of the leaves, convert- 

 ing them into fine saws. If loose 



pieces of such a leaf are shaken on a 

 flat surface they will move in the 

 direction opposed to the points of the 

 barbs. Such leaves are awkward to 

 eat, and if they are stroked the wrong 

 way they cut like a knife. 



There are some 3500 species. Ours 



Fig. 351.— Margin of a are all Small, but some of the bamboos 



11 tZl^'TiHo. reach a height of over 100 feet. This 



is one of the largest, and perhaps the 



most useful, of all the orders of plants. 



Zea 



Z. Mays (Maize). — This widely cultivated plant is 

 not a British species, but I mention it because the 

 male and female flowers are on different heads, some- 

 times, however, with a few male flowers among the 

 female, and female among the male. The male flowers 

 smell of cumarin, the female are scentless. It is only 

 partially self-fertile. 



Leersia 



L. oryzoides. — Besides the usual, there are cleisto- 

 gamous flowers, which are very small, and do not 

 generally emerge from the sheaths of the leaves.^ The 

 perfect flowers are rare, and still more rarely produce 

 seeds. 



Milium 

 M. efifusum is slightly protogynous. 



Setaria 

 S. verticillata — which is sometimes found in culti- 



' Douval-Joiive, Bull. Soc, Bot. France, 1863. 



