Two more entries in a useful genre -- the photo-essay which shows young children what to look for in nature. Russell is a more subdued narrator than Phyllis Busch whose Exploring as You Walk in the Meadow (p. 326, J-100) and . . . In the City (p. 480, J-150) gave children rather too many unnecessary instructions, but like Busch she limits herself largely to what can be observed and does not attempt to present information in a systematic way. The Winter guide points out nuts chewed by squirrels, several types of birds' nests and insects' egg cases and tells just enough about tracks in the snow to tantalize the reader with the possibility of learning ""to read the stories told by animal tracks."" Small Worlds is more focused in that it concentrates on the concepts of the microhabitat and microclimate -- using gall insects, leaf miners and caterpillars who live in fruit to illustrate the former and showing (less successfully) how the varied growth of algae, moss and lichen on trees can indicate the latter. Both volumes will have served their purpose if they stimulate more questions than they answer.