K.— BOTANY 235 



events are, I think, too apt to be conveniently dismissed as ' acts of God ' 

 in the comfortable beUef that the causes are beyond our responsibiHty or 

 control. But like our own droughts and floods they are in no small 

 degree capable of regulation by the proper utilisation of plant cover. 

 It is perhaps nothing more than the truth to assert that the provision of 

 wood for the smelting of iron on the Weald of Kent, or the maintenance 

 of the fuel supply for the salt pans of Droitwich has, inter alia, its reper- 

 cussions in our own water economy of to-day. It is now probably 

 recognised by many that these extremes of water supply are in large 

 measure the outcome of lack of vision in respect to the proper integration, 

 both spatial and temporal, of our exploitation of the soil surface. To-day, 

 however, we find that it is the engineer who has to be called in to mitigate 

 results rather than the biologist to remedy the cause. 



This is partly because the engineer's remedies, though extremely 

 costly, are usually more immediate in their results and certainly more 

 spectacular, but largely, I think, because botanical knowledge on the 

 applied side is inadequately organised to fulfil the important role it can 

 and should play in co-operation with the engineer for the communal 

 well-being. 



Professor F. W. Oliver pointed out, in reference to the reclamation of 

 foreshores, that the plastic plant can and does meet the constantly changing 

 impact of the forces of nature in a way which the dead material of the 

 engineer cannot hope to emulate, and at a far lower cost. But such 

 biological control demands not only a comprehensive knowledge of the 

 life histories of the species utilised but also an appreciation of the en- 

 vironmental factors dynamic as well as static that is summed up in the 

 phrase ecological foresight. As an example of the type of investigations 

 which are calculated to provide the necessary data one might cite the 

 studies of Professor Weaver and his colleagues on the root systems of 

 American prairie species and on the effectiveness of the plant cover in 

 the prevention of erosion. Mr. F. N. Ratcliffe's summary of the position 

 on the arid pastoral regions of South Australia has shown that the erosion 

 there is largely an outcome of overstocking with grazing animals, which 

 took no cognisance of the normal climatic fluctuations, with the result that 

 plant growth in dry seasons could not keep pace with the loss of protec- 

 tion from wind due to grazing. 



Another matter to which I should like to refer in this connection is the 

 much discussed question of the preservation of natural areas. The 

 public generally needs guidance on these matters which the student of 

 plant life should furnish. Owing to the widespread ignorance of biological 

 knowledge the dynamic character of vegetation is by no means widely 

 realised. There are indeed many educated people to-day who think 

 that to preserve an area all you need to do is to leave it alone. The fact 

 that your open downland, presented to the National Trust, may, if left 

 unhindered, ultimately cease to be downland and become woodland 

 with the loss perhaps of the very features for which the area was preserved, 

 is for most a novel concept. The transition phase between grassland 

 and woodland that we term open scrub is perhaps at once the richest in 

 species of flowers and insects of all our natural plant communities and 

 the most transient. To preserve such it is necessary to remove trees 

 and shrubs just at the period when they would appear to be approaching 



