2i8 THE POPULAR SCIENCE MONTHLY. 



far as we can see, are identical with, those under which the plant 

 grew in its home, it may for a time take a fresh, lease of life and 

 thrive with an undreamed-of energy. 



What did Anacharis find in the waters of England and the 

 Continent that it did not have at home, and why should its energy 

 begin to wane now ? 



In Australasia one of the most striking of these intruders is 

 sweet-brier. Introduced as a hedge plant, it has run over certain 

 lands like a weed, and disputes every acre of some arable plats. 

 From the facility with which it is j)ropagated it is almost in- 

 eradicable. There is something astounding in the manner in 

 which it gains and holds its ground. Gorse and brambles and 

 thistles are troublesome in some localities, and they prove much 

 less easy to control than in Europe. The effect produced on the 

 mind of the colonist by these intruding pests is everywhere the 

 same. Whenever, in an examination of the plants likely to be 

 worthy of trial in our American dry lands, the subject was men- 

 tioned by me to Australians, I was always enjoined to be cautious 

 as to what plants I might suggest for introduction from their 

 country into our own. My good friends insisted that it was bad 

 enough to have as pests the plants which come in witliout our 

 planning or choice, and this caution seems to me one which should 

 not be forgotten. 



It would take us too far from our path to inquire what can be 

 the possible reasons for such increase of vigor and fertility in 

 l^lants which are transferred to a new home. We should have to 

 examine all the suggestions which have been made, such as fresh 

 soil, new skies, more efficient animal friends, or less destructive 

 enemies. We should be obliged also to see whether the possible 

 wearing out of the energy of some of these plants after a time 

 might not be attributable to the decadence of vigor through un- 

 interrupted bud-propagation, and we should have to allude to 

 many other questions allied to these. But for this time fails. 



Lack of time also renders it impossible to deal w^ith the ques- 

 tions which attach themselves to our main question, especially as 

 to the limits of effect which cultivation may produce. We can 

 not touch the problem of inheritance of acquired peculiarities, or 

 the manner in which cultivation predisposes the plant to innu- 

 merable modifications. Two of these modifications may be men- 

 tioned in passing, because they serve to exemplify the practical 

 character of our subject. 



Cultivation brings about in plants very curious morphological 

 changes. For example, in the case of a well-known vegetable the 

 number of metamorphosed type-leaves forming the ovary is two, 

 and yet under cultivation the number increases irregularly until 

 the full number of units in the type of the flower is reached. 



