LIST OF PLATES 



FRONTISPIECE. Attraction for pollinating insects in Cornus canadensis, 

 a shade plant of cold woods with inconspicuous perianth, but a large 

 and showy white involucre, the whole head appearing like a flower. 



Facing page 

 PLATE I. Sand dunes with sea rye grass (Elymus arenarius). A sand 



binder, deep-rooted, with extensively running rootstocks .... 52 



PLATE II. Exposure of leaves to sunlight. All the leaves are arranged 

 at such an angle as to receive the maximum illumination. Balsam 

 spruce forest along a brookside, east slope of Pikes Peak. Species 

 represented : Actoea eburnea. Chamcenerion angust (folium, Hera- 

 cleum lanatum. Hubus strigosus 94 



PLATE III. Cypress swamp, with Spanish moss ( Tillandsia), an epiphytic 

 seed plant practically leafless, the work ordinarily done by leaves . 

 devolving on the slender stems. The cypress trees are furnished 

 with ''knees, 1 ' or projections from the roots, which are thought 

 by some to absorb air 110 



PLATE IV. Rockweeds exposed at low tide 204 



PLATE V. A common tree lichen (Physcia stellar is) 254 



PLATE VI. A wound parasite (Pleurotus ulmarius) on a maple tree . 270 

 PLATE VII. Tree ferns (Dicksonia antarctica) from Tasmania . . . 310 

 PLATE VIII. A probable landscape in the Carboniferous Age . . . 340 



PLATE IX. Belt of trees along a Nebraska river, showing dependence 



of forest on water supply. 

 Xerophytic grasses on Nebraska sand hills 462 



PLATE X. Zonation about a pond in southwestern Ohio. The plate 

 shows the north end of a pond of about eleven acres in area par- 

 tially surrounded by seven zones beginning with submerged aquatics 

 and ending with a forest zone (in the portion next the pond, mainly 

 of maples, elms, ashes, and willows) 478 



PLATE XI. Leaning trees at timber line on Pikes Peak 486 



PLATE XII. A coniferous forest interior of central Colorado. The trees 

 are Douglas spruce (Pseudotsuga mucronata). The light intensity 

 is so feeble, from the dense shade, that the only seed plants on the 

 forest floor are saprophytic or parasitic orchids and a few little 

 Pyrolas 494 



PLATE XIII. A tropical forest in the Philippines, showing characteris- 

 tic dense vegetation, the trees of many species, mostly palms . . 518 



ix 



