CHAP, ii.] of Plants. Ccsalpino. 453 



it be the ratio vacui ; for since not moisture only but air also 

 is contained in the earth, the plant would be filled not with 

 juice but with air. But Cesalpino hits upon a third kind of 

 cause by which juices may be drawn into the plant. Do not 

 many dry things, he says, in accordance with their nature 

 attract moisture, as linen, sponge and powder, while others 

 repel it, as the feathers of many birds and the herb Adiantum, 

 which are not wetted even when dipped in water; but the 

 former absorb much water, because they have more in com- 

 mon with it than with air ; of this kind Cesalpino thinks those 

 parts of plants must be, which the nourishing soul employs to 

 take in food. Therefore these organs are not traversed by a 

 continuous canal such as the veins in animals, but formed like 

 the nerves of a fibrous substance ; and thus the power of 

 suction (bibula natura) conveys the moisture continually to 

 the place, where the principle of internal heat is placed, just as 

 may be seen in the flame of a lantern, to which the wick 

 continually conducts the oil. The absorption of the moisture 

 is also increased by the outer warmth, for which reason plants 

 grow more vigorously in spring and summer. 



That Cesalpino had no suspicion of the use of the leaves in 

 the nutrition of plants appears incontestably from his repeat- 

 ing the Aristotelian idea, that the leaves are only for the 

 protection of young shoots and fruits from air and sun-light ; 

 this idea is no result of speculation, but came simply from 

 observing a vineyard in a hot country. 



2. FIRST INDUCTIVE EXPERIMENTS AND OPENING OF NEW 

 POINTS OF VIEW IN THE HlSTORY OF THE THEORY OF 

 THE NUTRITION OF PLANTS. 



ALL that Aristotle and his school, Cesalpino not excepted, are 

 able to tell us about the phenomena of vegetable life, was the 

 result of the most every-day observations, none of which were 

 critically and exactly tested to ascertain their actual correctness, 



