LABORATORY AND FIELD WORK 265 



of leaves there are in the greenhouses and to explain their ecological 

 significance. 



5. To discover how many symbiotic i)henomena are in evidence 

 in a wood-lot during winter. 



Ecological Anatomy.— Studies in ecological anatomy nnist be 

 carried on largely in the laboratory. Since leaves are much more 

 plastic than roots and stems more time is devoted to them. The 

 few problems stated below will serve to suggest others. 



Suggested Problems 



1. To make a comparison between the stem and root of a mesic 

 plant as to internal structure, and to explain the ecological sig- 

 nificance of the differences. 



2. To make a comparison between a rhizome and a root as to 

 internal structure. 



3. To discover which of the leaves provided is mesic, which xeric, 

 and w4iich hydric. (Students should cut their own sections if possi- 

 ble, but if time or facilities do not permit this, prepared slides may 

 be used.) 



4. To discover which of the leaves provided is a sun leaf and which 

 a shade leaf. (Sun and shade leaves of hard maple make good 

 material for this.) 



5. To classify each of the leaves studied as diphotophyll, diplo- 

 phyll, staurophyll, or spongophyll. 



Symbiotic Phenomena.— The studies that may be made of 

 symbiotic phenomena are almost unlimited. It is well to advise 

 students to be on the look-out for symbiotic relations on all field 

 trips made in addition to making some trips especially for these 

 studies. Numerous structures resulting from symbiosis make good 

 material for laboratory work. 



Suggested Problems 



1 . To discover how a dodder plant obtains food from its host. 



2. To discover what kinds of trees in a wood-lot have ectotrophic 

 mvcorrhizas. 



3. To compare the mycorrhizas of a hickory tree with those of an 

 orchid. 



4. To make a list of the lianas in a wood-lot and discover w^hich 

 ones twine in a clockwise and which in a counterclockwise direction. 



