io6 NATURAL SCIENCE. August, 1895. 



subsequent generations reproduce these characters of sexless origin 

 by means of seeds." 



Mr. Bailey further observes that, since evolution by asexual 

 variation can take place under cultivation, it will be able to do so in 

 nature, whenever plants can be multiplied and distributed by detach- 

 ments from their vegetative system, as many water plants are [Hydro- 

 chavis, Elodea, etc.), and numerous land plants, by bulbils, runners, 

 offsets, etc. 



Darwin has collected a number of instances of " bud-variation 

 by suckers, tubers, and bulbs,"^ as among potatoes, dahlias, phlox, 

 tulips, etc. Since, therefore, new varieties and races can be 

 established by bud-variation alone, there is ample evidence to prove 

 that " a progressive evolution of plants can take place without the 

 aid of sex." 



The rationale of all this is, that variation in plants is always due, 

 directly or indirectly, to the influence of the environment ; and it 

 matters not whether the plant be raised from seed or from the 

 vegetative system, the new surroundings can act on both precisely in 

 the same way. This, I have proved, e.g., taking slips and seed 

 from the wild spiny rest-harrow, in two years I have converted 

 both into a spineless form not distinguishable from the so-called 

 species Ononis repens, L, by growing them in a constantly saturated 

 atmosphere. 



Mr. Bailey concludes his article by refuting Dr. Weismann's 

 theory and observes : " I should bring in rebuttal the result of direct 

 observation and experiment to show that given hereditable asexual 

 variations are often the direct result of climate, soil, or other impin- 

 ging conditions. As a matter of fact, we know that acquired characters 

 may be hereditary in plants ; if the facts do not agree with the 

 hypothesis, so much the worse for the hypothesis." 



Now it is in this power of evolution, in the vegetable kingdom, 

 by wholly sexless means, that Mr. Bailey sees a fundamental differ- 

 ence between the evolution of plants and that of the higher animals 

 at least. 



George Henslow. 



^Op. cit., i., p. 384. 



