CHAPTER V 
PLANT STRUCTURES 
In the course of the preceding chapters a number of 
the more striking modifications displayed by the 
different organs of plants have been described briefly. 
Reference has been made to the increased length or 
thickness of the roots in plants of dry places, and the 
weakness or absence of root-system of many water 
plants. Corresponding variation in stems has been 
noted. The remarkable leaves of desert and water 
plants and of some carnivorous species have been 
mentioned. The profound alteration in flowers which 
have adapted themselves to pollination by insects has 
been sketched; as also the great variety in the shapes 
of fruits and seeds, correlated to the methods by which 
they are dispersed. It may be well to consider the 
question of plant structures on a broader and more 
systematic basis, and, as before, to connect them where 
possible with the external factors which have caused 
their modification and to which they are the plant’s 
response. These factors are physical, or chemical, or 
biological, and affect the plant mainly through the 
agency of the soil, the atmosphere, or living 
organisms. 
“The living plant is a synthetic machine.” Under 
proper working conditions of heat, moisture, and light 
it builds up its body by absorption of inorganic 
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