26 NEW ZEALAND PLANTS. 
plants of dry ground); they may have no root-hairs at all (as in 
many swamp-plants): all the above are adaptations connected with 
the water-supply. 
The size, thickness, position with regard to the sun, flatness, 
degree of closeness at which they are given off from the stem, hairi- 
ness, glossiness, and other characteristics of leaves have a special 
bearing with regard to the amount of water which evaporates from 
them or which they have stored up in their tissues. Many of the 
different degrees of development which leaves assume with regard 
to the characters cited above can frequently, with some degree of 
confidence, be looked upon as adaptations. It is very easy to 
carry the idea of adaptations too far, and to use the imagina- 
tion rather than reason based on observation and—best of all—on 
experiment. Even with the latter, where living plants in their 
natural habitats are concerned, it is almost impossible to devise 
experiments which can say that one particular agent is the actual 
cause. More satisfactory experiments can be carried out in the 
laboratory ; but it must never be forgotten that the conclusions 
derived from such refer only to the plant under the laboratory 
conditions and not to the plant in the field. All this might make 
one feel rather pessimistic regarding studies of the living plant in 
nature; but pessimism need not raise its horrid head—in general, 
plants have already told a good deal. Observation pure and simple 
is a tool of power which lies ready to the hand of all. Nature is 
carrying on her work now as in days primeval; much can be 
learned by an ardent student in her workshop. 
