THE PRESIDENTIAL ADDRESS. 3 



its own independent course, with increasing size and complexity of the 

 individual. In tracing this I would ask your special attention this evening 

 to the Kingdom of Plants. 



The first of the laws laid down by Lamarck ^ in his Histoire Naturelle 

 as fundamental in the evolution of animals and plants ran thus : ' Life 

 by its intrinsic forces tends to increase the volume of every living body, 

 and to enlarge its parts up to a limit which it determines itself.' When 

 in unicellular organisms, following this law, a certain size has been reached, 

 fission follows, and the equal halves separate as new individuals. In 

 pluricellular bodies, however, the products of cell-division do not separate, 

 but continue a communal life ; and the individual may increase, with 

 further division of its cells, to large size and complexity. We may picture 

 how, based upon the mobile stage of a Flagellate, the aggregate might 

 form an animal body with motility as a leading featiire ; on the other 

 hand, based upon the sedentary stage, an immobile plant-body would 

 result. The animal, adopting a predatory habit and colourless, might 

 progress along lines of dependent nutrition, finding and ingesting food 

 already organised ; the sedentary green plant might evolve along lines 

 of physiological independence, constructing its own organic supplies. 

 Whether or not this be a true picture, the whole organisation of the two 

 kingdoms diverged on the basis of nutrition. Herbert Spencer contrasted 

 them physiologically, showing how animals are expenders, while plants 

 are accumulators ; that the former are limited in their growth by the 

 balance of expenditure against nutrition ; in the latter growth is not so 

 limited. Thus, the problems that follow on increasing size may be expected 

 to work out differently in view of the animal kingdom comprising organisms 

 of high expenditure and not self-nourishing, while plants are self-nourishing 

 accumulators. 



The result of this difference may be illustrated by contrasting some of 

 the highest examples of either kingdom ; for instance, the elephant, with 

 the trees of the forest through which he roams. On the one hand, the 

 relative fewness of the mobile elephants, their less stature and compact 

 form, their columnar legs needed to support the barrel-like body, the 

 receptacle for ingested food, the economy of external surface and the 

 highly developed internal surfaces. On the other hand, the height, 

 immobility and large number of the trees, with their massive stems and 



• Lamarck died in 1829, and the Association has contributed to a fund being 

 raised for a Memorial by the Linnaen Society of Northern France. 



B 2 



