PHYSICAL FACTORS IN PLANT DISTRIBUTION 67 



graphical ranks toward the accumulation of further raw mate- 

 rials or else, on the opposite side of the field, are advancing from 

 the physiological outposts to attack specific problems. In spite 

 of the wide separation of these attacking forces there exists 

 between them the best of understanding and the most helpful 

 of communication. There is urgent need that this be the case, 

 for the field is large and the attack must be a prolonged one. 

 With co-operation between different parts of the field and co- 

 ordination of effort throughout the campaign, we can look for- 

 ward to the daily enjoyment of victory in a conquest which is 

 almost without bounds. 



/s 



^^t 



