'NATURAL SELECTION " AND "SURVIVAL OF THE FITTEST." 93 



ditch, is on one side of a well-trodden footpath ; on the other is a strip of 

 grass, say one foot in width, then comes the road sloping gently down to 

 the latter, forming a little damp trough or gutter. Close under the 

 hedge, where it is excessively dry, may be a long strip of Hordeum 

 murinum, Bromus sterilis, or Holcus lanatus. All three are hairy, 

 xerophytic grasses. On the other hand, the strip by the roadside, where 

 it is damp, will be usually some such grass as rye-grass (Lolium perenne). 

 In the little gutter itself may be plantains or silver-weed. 



Hence, while the hedge and its companions are xerophytes, the 

 lolium and the last mentioned are mesophytes.* Here again, the grains 

 of the xerophytic and moisture-requiring grasses must reach each other's 

 domains, being only the breadth of the footpath asunder, yet they keep 

 true to their respective sides. 



One may often see natural selection well illustrated in a garden, if it 

 be at all neglected. I will give two of my own experiences. Having a 

 bare piece of ground under some trees, I sowed it with "tennis-lawn" 

 grass, and sprinkled sifted earth over it. The latter happened to have a 

 gcod deal of cbickweed seed in it, which came up with the grass and 

 practically smothered it. Raking it off before the latter was injured, the 

 grass grew well enough, but the locality proved to be too shady, and most 

 of the grass ultimately died, the sole exception being cock's-foot (Dactylis 

 glomerata), which grew in isolated tufts. The whole place was finally 

 invaded by red campion (Lychnis dioica) from the adjoining shrubbery. 



In another garden belonging to a house which was sold in the summer, 

 the usual seed-crops had been sown in the spring, but were subsequently 

 neglected. I wandered through it on the day of the sale and found all 

 the crops of peas, &c, perishing in the struggle for life with chickweed, 

 Solarium nigrum, Urtica urens, groundsel and Poa annua. These 

 annuals had it all their own way, and the crops were ruined. 



The last-mentioned grass is interesting. I made a lawn with turf cut 

 from a hayfield in which was no Poa annua at all. A good deal of this 

 grass grew in the garden as a weed in the borders and paths. It soon 

 invaded the lawn, which was kept well mown. Gradually the perennial 

 grasses disappeared till the lawn was almost entirely composed of Poa 

 annua. It seeded profusely and became a perennial, the turf being 

 perfectly good all through the winter. 



Other illustrations of natural selection may be taken from the 

 behaviour of certain British wild flowers accidentally or otherwise in- 

 troduced into our Colonies. Ne*w Zealand has been especially studied in 

 this respect. The following details are taken from Mr. Thomas Kirk's 

 report on " The Displacement of Species in New Zealand." f 



The author first supplies a list of species recorded as introduced, as 

 follows:— In 1855, 41; 1867, 150; 1869,251; 1872,264; 1888, 385; 

 1896, 500. 



On sea-beaches, native plants have been crowded out by Bromus 

 sterilis, Rumex obtusifolius, B. crispus, Erigeron canadense, Silene 

 anglica, Holcus lanatus, kc. 



* I.e. intermediate between drought-plants or xerophytes and plants requiring 

 moisture or hygrophytes. 



f Trans. New Zealand Institute, vol. xxviii., 1896. 



