ECOLOGICAL GROUPS 



489 



Make a list of all the aquatic seed plants that j'ou know, 

 of some of the principal marsh plants, of several herbaceous 

 and several woody mesophytes, of all the xerophytes you know, 

 — the xerophytes arranged somewhat in the order of their 

 capacity to resist drought conditions. 



447. Ecological groups based on light relations. Plants 

 which prepare their food by photosynthesis evidently need 



Fig. 367. Spanish moss (TiUandsia) 

 growing on branches of a tree 



Much reduced. Photograph by 

 S. M. Tracy 



Fig. 368. Tufts of Spanish moss, with 

 leaves of the magnolia on which it grew 



Reduced. Photograph by Florida Agri- 

 cultural Experiment Station 



light as much as they do air or water; but there is great 

 diversity in their demands as regards intensity of light. The 

 practical forester soon becomes familiar with this fact, and 

 the gardener and floriculturist know that while some plants, 

 such as tulips, poppies, verbenas, and most composites, need 

 all the sun they can get, other plants, as most ferns, lilies of 

 the valley, spiderworts, many violets, many genera of the Pars- 

 ley family and the Heath family, grow best in partial shade. 



