148 BRITISH PLANTS 
staple food of the people living on the dry plains of India 
and China; African millet (Dhurra, Guinea or Kaffir corn) 
is Sorghum vulgare. Maize (Zea Mais) contains more 
sugar and oil than most cereals; it is the only cereal 
which we owe to America; in South Africa it is called 
** mealies.” 
Wheat is the most valuable of all the cereals, and the 
general demand for it among the more prosperous of 
mankind is increasing every year. Besides starch, flour 
contains protein and a small quantity of oil. If flour is 
kneaded with water, the starch can be separated and 
pressed out through muslin, and the stringy, sticky mass 
left behind is gluten, which consists largely of protein. 
A large part of the protein in wheat is contained in a 
special layer of cells lying close to the surface of the grain. 
In the best white flour this is removed with the outside 
husk, with the result that the flour is deprived of a large 
part of its nourishing qualities. 
Oily Seeds are of more importance to man as a source 
of oil, extracted for economic purposes, than as food— 
e.g., cotton-seed-oil, coconut-oil, palm-oil for soap-making, 
castor-oil, coco-butter, linseed-oil from flax-seed, rape and 
colza-oil from rape-seed. 
The seeds of Sinapis yield mustard, and from the seeds 
of Strychnos Nux-vomica, strychnin, a deadly poison, is 
obtained. 
2. Fruits.—Fruits in which any considerable quantity 
of food-stuff is stored are fleshy. These fruits are par- 
ticularly adapted to attract the attention of birds and 
provide them with food, but the seeds are preserved from 
destruction either by being hard and indigestible, or by 
being enclosed in hard shells (p. 136). The formation of 
large fleshy fruits seems at first sight a very extravagant 
means of providing for the dispersal of the seed, but the 
method is an extremely efficient one, for there are few 
other means by which seeds can be carried so far or 
distributed over so wide an area as by birds. 
Cultivated Fruits——Many succulent fruits have been 
cultivated by man from very early times, and in the 
Tropics some, like the banana, form his staple diet. 
Other examples are apples, pears, plums, cherries, apricots, 
peaches, gooseberries, blackberries, raspberries, red and 
white currants, grapes, strawberries, oranges, lemons, figs, 
