APPENDIX R 



545 



CEREAL GRAINS. 



By far the most important vegetable foods are the Cereal Grains, 

 which are the fruits of various Grasses (Graraineae). The general con- 

 struction of all of these grains is the same, and the structure of the grain 

 of \Mieat will ser\-e to illustrate it for them all. 



The Wheat-Grain is oval, and haiiy at the apical end, but smooth 

 at the base where is the scar of attachment. A lateral groove running 

 longitudinally marks the pos- 

 .terior side ; the anterior side 

 is convex, and shows near its 

 base an area which is de- 

 pressed and wrinkled when 

 dr\-. This marks the position 

 of the germ, which is thus 

 basal and faces the anterior 

 side of the grain (Fig. 446). 

 The greater part of the grain 

 is made up of a mass of eudo- 

 sperin : this together ^^ith the 

 germ is covered by the fruit- 

 coat (pericarp) and seed-coat 

 (testa), which jointh- form a 

 hard brittle shell, separated in 

 milling from the inner parts 

 as Bran. 



A microscopic examination 

 shows that the gerni consists 

 of thin-waUed tissue densely 

 stored ^^-ith oily protoplasm, 

 but ^^•ith no starch. The cndo- 

 sper))i is also thin-walled, but 

 contains much starch closelv 

 packed (Fig. 447, am) ; but a 

 superficial layer of its cells is 

 distinguished by the absence 

 of starch, while as it contains numerous aleurone grains it is recognised 

 as the aleurone-layer (al). The Bran consists of compressed and 

 thickened cell-walls of icoodv texture, containing a deposit of silica. 

 The outer band (p) represents the fruit-coat or pericarp : the inner 

 (t) represents the seed-coat or testa. 



The constitution of the "\Mieat-Grain as sho-wn bv analvsis may ^-ar^- 

 considerably according to sample. This is sho-s^-n even in so important 

 a feature as the proportion of nitrogenous substances. " Soft \Mieat " 

 may contain only io-8o per cent, of proteid, while " Hard Wheat " has 

 been found to contain 13-83 per cent. In some Russian ^^^leats it 

 may even rise above 17 per cent. These facts are mentioned to sho-w 

 that the results of analysis must be taken as a general guide rather than 

 as a statement of constant fact. 



Fig. 446. 



Part of a median longitudinal section of a grain of 

 \^"heat, showing embryo and scutellum (sc). vs =vasc. 

 bundle of scutellum; cc=its columnar epithelium; 

 r^ligule; c=sheathing part of cotyledon; ^y=vege- 

 tative cone of stem; /z^^ =h\"pocotyl ; /=epiblast; 

 r=radicle; c/ =root-sbeath ; fjz = micropyle ; / = funi- 

 culus ; I'/) = vascular bundle of funiculus; / = lateral 

 wall of groove; f/i = peri carp. ( \ 14.) (.\fter Stras- 

 buxger.l 



