THE ORGANIZATION OF PLANTS INTO SOCIETIES 61 
Do any stomata have special structures for protection? 
Which leaves are compact? Do any have regions or 
cells for air or for storage of water or food? 
Show of what advantage, if any, the different structures 
observed are to the plants as they attempt to live in their 
respective environments. 
Roots.—Note the variations in the general form of the 
root system. Do hydrophytes, as a rule, have their roots 
spreading or running deep into the ground? How about 
plants of dry regions? Are root-hairs developed in equal 
abundance in all these regions? Explain any variations. 
To make quite clear in what particulars some plants are 
especially fitted to the regions in which they are found, 
imagine a water-lily and a cactus to change places, and show 
‘ why each would probably fail to succeed in the region of the 
other. 
From the above it must not be inferred that all plants 
are by any means perfectly adapted to their habitats. Some 
are so far from this condition that they can scarcely exist, 
grow poorly, and reproduce themselves in a meager way. 
Neither must it be inferred that a plant once a hydro- 
phyte is always such. Some plants are hydrophytes part 
of the time and mesophytes or xerophytes the rest of the 
year. It is to be noted, for example, that a high tempera- 
ture and abundant moisture make hydrophytic conditions, 
while high temperature and dearth of water make desert 
or xerophytic conditions. Such regions present each of 
these combinations at different times of the year, and there 
are plants adapted to living in these regions the year 
around. 
Suggestions for further work.—Outlines for work may 
well be planned upon mesophytic societies, comparing them 
with hydrophytes and xerophytes. A study of a forest com- 
munity will prove profitable. Deserts, heaths, and tropical 
communities illustrated by native plants or those found in 
