Tiic Roots of the JJlieat Plant. 



185 



diameters, we shall be able clearly 

 to make out the stomata or breath- 

 ing pores by Avliicli the leaf is 

 dotted. — (Diagram 7.) 



Now what we should here 

 notice, is that as the wheat-plant 

 grows upright leaves, and does 

 not, like the turnip, present a flat 

 under-side of these organs to the 

 ground, so the stomata in uiheat 

 arc as thick on one side of the leaf 

 as on the other, a condition com- 

 mon to other upright growing 

 plants, as the iris, pink, and the 

 like. 



The first sight, however, of a 

 turnip-leaf shows that it differs 

 greatly in this respect from that 

 of the leaf of the wheat : the 

 lighter colour of its under part 

 evidencing that a very large ma- 

 jority of these pores are situate 

 on the under as compared with 

 the upper side. — (Diagram 8.) 



If, then, we for a moment con- 

 sider that the leaves are 

 the respiratory organs 

 of plants, that they are 

 concerned in the fixa- 

 tion of carbon and per- 

 haps we may add of 

 nitrogen, and that it is 

 through the stomata 

 that the carbonic acid 

 for the carbon if not 

 the ammonia for the 

 nitrogen is respired, 

 we shall, 1 think, be 

 able to explain why the 

 surrounding the wheat- 

 plant with ammoniacal 

 manures -at the season 

 of its most vigorous 

 growth may be produc- 

 tive of benefit ; and 

 though we may in part 



Diagram 7 — Stomata of Wheat, 

 about 250 diameters, 2^9. 



Diagram 3— Stomata of Turnip, under side, 

 about 250 diameters, ids. 



