LEAVES IN SEASONS 153 



The chlorophyll is not found in the organisms 

 where the two kingdoms meet, but occurs in 

 animals which have attained a high degree 

 of development, such as the vorticella, and 

 fresh-water sponges. It is supposed that the 

 chloroplasts in these animals are descended 

 from others derived from unicellular plants 

 captured by the animals in an earlier stage 

 of the development. 



To a naturalist one of the striking and 

 spectacular features in the history of living 

 things is the manner in which vegetation puts 

 on, wears, and discards its leafy coverings of 

 green. The season begins with the assump- 

 tion of an all prevalent, delicate green cover- Autumnal 

 ing, composed of millions of irregular laminae icaf-faU 

 of every conceivable form, which hide the 

 roughnesses of gnarled and crooked branches, 

 the flinty soil and ragged moor. With the 

 advancement of the leaves toward maturity, 

 the earlier and more delicate tint deepens into 

 a rich satisfying green that fills the eye, and 

 then fades away in the long summer heat to 

 dull gray and bluish greens, dust-colored and 

 bearing the marks of many subduing strug- 

 gles with wind and storm. The first breath 

 of frost is the signal for a change on slopes, 

 valleys, forests and meadows, by which the 

 dull monotones are at once converted into a 



