The _autumn colors_ are due to intermingled shades of green, yellow, and red. The coloration varies with the kind of plant, the special location, and the season. Even in the same species or kind, individual plants differ in color; and this individuality usually distinguishes the plant year by year. That is, an oak which is maroon red this autumn is likely to exhibit that range of color every year. The autumn color is associated with the natural maturity and death of the leaf, but it is most brilliant in long and open falls--largely because the foliage ripens more gradually and persists longer in such seasons. It is probable that the autumn tints are of no utility to the plant. _Autumn colors are not caused by frost._ Because of the long, dry falls and the great variety of plants, the autumnal color of the American landscape is phenomenal. =Ecology.=--The study of the relationships of plants and animals to each other and to seasons and environments is known as =ecology= (still written _œcology_ in the dictionaries). It considers the habits, habitats, and modes of life of living things--the places in which they grow, how they migrate or are disseminated, means of collecting food, their times and seasons of flowering, producing young, and the like. SUGGESTIONS.--One of the best of all subjects for school instruction in botany is the study of plant societies. It adds definiteness and zest to excursions. =7.= Let each excursion be confined to one or two societies. Visit one day a swamp, another day a forest, another a pasture or meadow, another a roadside, another a weedy field, another a cliff or ravine. Visit shores whenever possible. Each pupil should be assigned a bit of ground--say 10 or 20 ft. square--for special study. He should make a list showing (1) how many kinds of plants it contains, (2) the relative abundance of each. The lists secured in different regions should be compared. It does not matter greatly if the pupil does not know all the plants. He may count the kinds without knowing the names. It is a good plan for the pupil to make a dried specimen of each kind for reference. The pupil should endeavor to discover why the plants grow as they do. Note what kinds of plants grow next each other; and which are undergrowth and which overgrowth; and which are erect and which wide-spreading. _Challenge every plant society._ CHAPTER V THE PLANT BODY =The Parts of a Plant.=--Our familiar plants are made up of several distinct parts. The most prominent of these parts are _root_, _stem_, _leaf_, _flower_, _fruit_, _and seed_. _Familiar plants differ wonderfully in size and shape_,--from fragile mushrooms, delicate waterweeds and pond-scums, to floating leaves, soft grasses, coarse weeds, tall bushes, slender climbers, gigantic trees, and hanging moss.