LECTURE II 



THE EFFECT OF A FIXED POSITION ON THE 

 SEXUALITY OF PLANTS 



IF an average man were asked what is the most striking 

 difference between Animals and Plants, he would probably 

 reply that Animals move and Plants do not. But this 

 would be an over-statement of the real facts. Living 

 Plants do move, though their movements are slow and 

 constrained. No organic Life is possible without move- 

 ment of one sort or another. But there is an essential 

 difference of structure between Animals and Plants which 

 explains their respective powers of movement. The 

 protoplasm of the former is not as a rule confined within 

 a wall, and tissues-masses composed of such cells can 

 move freely, as our own muscles do. But each of the cells 

 of the Plant is enclosed in a resistant cell-wall, which 

 checks the mobile protoplasm within, and at the best its 

 movements are only slow. Plants have in fact bartered 

 their free motility for the protection given by the cell- 

 wall. Already Euglena shows in its temporary encysted 

 stage the condition usual in the plant-body (Fig. 3, D) ; 

 but the cell-wall is a permanent feature in such simple 

 plants as Protococcus tfiridis (Fig. 5) ; and in Ulothrix 

 (Fig. 6, A) it is also, except in its propagative phase. 

 The further circumstance that Plants are habitually fixed 



