Natural History 601 



myriads of birds formed the nitrate beds of Chili, and the nitrogen 

 atoms of these salts scattered on the wheat fields appear again in 

 another grouping in the gluten of bread. The animal dies and 

 sinks to the earth ; its body is buried by sexton-beetles ; the bacteria 

 which cause all putrefaction break down the tissues into simple 

 chemicals, which plants once more reincarnate in the cycle of 

 life. 



In the article on BACTERIA it will be shown that these 

 microbes have their finger in many a pie. They are the smallest 

 plants, but their role in the economy of nature is of incalculable 

 importance. If green plants be called the "producers," and ani- 

 mals the "consumers," bacteria are the "middlemen." 



But we must also recognise the significance of the microscopic 

 green plants of the sea and the freshwaters. Diatoms enclosed in 

 exquisitely sculptured shells of flint (see illustration opposite 

 page 318), and the hardly less beautiful Desmids, swarm 

 in inconceivable numbers in the surface waters, along with 

 other simple Alga? (and some microscopic green animals as well) ; 

 and they constitute the fundamental food-supply of higher 

 forms of life. All of them are absorbing air, water, and salts; 

 all of them are splitting up carbon dioxide, liberating oxy- 

 gen, and building up carbon compounds: they make higher life 

 possible. The microscopic specks are not less important 

 than the great seaweeds. If "all flesh is grass," then "all fish 

 is diatom and sea-dust." In the springtime the surface waters 

 of the lake are sometimes green and almost soup-like in 

 the density of their Alga population, and the silent crowded 

 turbulence is spoken of as "the breaking of the meres." A bucket 

 of water lifted from the open sea may contain minute plants far 

 more numerous than the stars we can count on a clear night. 



Variety of Plant Life 



There is a long gamut from the diatoms specks of living 

 matter, in beautiful shells of flint to the daisy, from the hyssop 



