THE AMERICAN BOTANIST 47 



Several explanations of these and other phenomena have been 

 advanced. The commonest one is that the plant is introduced 

 but its fungous and insect enemies are not. Therefore the 

 plant is released from all handicaps as it were and can exer- 

 cise to the utmost its inherent energy. A second and related 

 explanation is that every plant becomes held within limits by 

 the competition of other plants in its native land and very often 

 in the new environment the native plants do not have an equal 

 restraining influence — because they have had to contend with 

 a different set of competitors A third idea is that any organ- 

 ism with the ability to spread at all becomes more energetic 

 through the constant mixing of blood of the advancing popula- 

 tion. All these ideas are interesting, but difficult if not impos- 

 sible of experimental proof. The last suggestion receives some 

 support from the fact that many weeds and other organisms 

 run out after they have ceased to spread. The recent examples 

 of the Russian thistle and the prickly lettuce are familiar 

 cases. Such phenomena may be due wholly or in part to in- 

 crease in enemies, but in many cases like the two cited there is 

 not one iota of positive evidence. I think we ought to give 

 such phenomena more consideration as they reveal traits in 

 plants that transcent all our sterotyped and inadequate theories. 

 The old gardener often treats his plants as if he regarded them 

 as sentient beings. Perhaps we err in considering them too 

 much machines. — C. V. Piper in Science. 



Natures Planting. — When planting our flower gardens 

 we rarely plant as thickly or mix things up as thoroughly, as 

 Nature does in her wild planting. A writer in the Garden 

 Magaciiie notes that in a single square foot of prairie sod he 

 found five shooting stars, one purple rudbeckia, six spikes of 

 phlox, three wnld hyacinths, one aster, five clumps of blue-eyed 

 grass, two clumps of yellow star-grass and one clump of bird's- 



