1876.] 



AND HORTICULTURIST. 



343 



means the case. The leaves only become active 

 after the shoot has attained its full development. 

 Until this point is reached, the leaves them- 

 selves, as well as the axis of the shoot, need 

 nourishment, in order to enable them to reach 

 their natural size, and finally fit them for the 

 work of assimilation." 



[The writer of this can confirm Professor 

 Koch's views. In experimenting years ago, he 

 would pick off the leaves of the pushing young 

 branches of Ashes, Horse-Chestnuts, and Maples, 

 as fast as they could be discerned. Nevertheless 

 the shoots would become wood to a consider- 

 able portion of the whole length. The material 

 for the organization must have been partly 

 stored up the previous year, and partly drawn 

 from other parts of the plant. — Ed. G. M.] 



The Warfare of Plants on one Another. — 

 Mr. Lester Ward in the Popular Science Monthly 

 for October, has the following good piece of 

 reasoning : — 



" The most frequent and prominent cause 

 of these disturbances of the natural fixity 

 of vegetation is the influence of man. The re- 

 sults of this influence may be said to be the pro- 

 ducts of agriculture, horticulture, and floricul- 

 ture, on the one hand; and, on the other, weeds. 

 But there may be many other causes of dis- 

 turbance besides that produced by man, such 

 as the appearance of new animals, geological 

 revolutions, or climatal and meteorological vicis- 

 situdes. Anything which destroys the stability 

 which the perpetually-operating vegetal forces 

 impose upon the plants of any region is certain 

 to reveal a latent vitality, which, when liberated, 

 proves itself capable of profiting by conditiuns 

 far different from, and superior to, those under 

 which it is originally found. The willow, the 

 alder, the elm, and the sycamore, hug the banks 

 of streams because baffled and beaten back at 

 every attempt to invade the drier ground. The 

 wild-columbine and the saxifrage are driven in- 

 to their rocky fastnesses by more powerful rivals 

 for the rich forest loams. The thistle and the 

 chamomile flourish in lawns and commons, be- 

 cause their human foes are less formidable than 

 the enemies of the plain. The fruit-trees, the 

 cereals, and the roses, reach those wonderful 

 heights of development under man's care, be- 

 cause he not only proves their friend, but wards 

 off" all their enemies. And just here it should be 

 remarked that the alleged tendency of culti- 

 vated plants to relapse, when neglected, into 

 their original state, upon which Prof. Agassiz 



laid so much stress as an unanswerable argu- 

 ment against transmutation, becomes, under the 

 law of mutual repulsion, the necessary result of 

 remanding them to their old conditions. As 

 man's care and protection were necessary to 

 enable them to advance, so, when these are 

 withdrawn, they rnust be expected to again yield 

 to hostile forces, and fall back to the level of 

 their original state." 



[We have long known that cultivated plants do 

 not necessarily go back, as Agassiz urged against 

 Darwin, when left to themselves. Varieties 

 raised under culture reproduce themselves from 

 seed just as well as true species, and we believe 

 that so far as any inherent law is concerned, 

 would go in with the ages just as well. They 

 are crowded out by more powerful rivals. — Ed. 

 G. M.] 



Adaptation to the Environment. — It has 

 long been regarded as a law of life, applicable 

 alike to animal and vegetable forms, that each 

 species is exactly adapted to the particular habitat 

 where it occui's ; and naturalists, assuming this 

 law, have sought to solve the problem how this 

 remarkable adaptation has been brought about, 

 instead of pausing to question the alleged law of 

 adaptation itself. And yet there have never 

 been wanting numerous and obvious facts, espe- 

 cially in the vegetable kingdom, which, if inter- 

 preted at all, must be conceded to be incompati- 

 ble with such a law, at least unless materially 

 modified and greatly enlarged. 



Mr. Thomas Meehan has remarked the fact 

 that " almost all of our swamp-trees grow much 

 better when they are transferred to drier places, 

 provided the land is of fair quality. He referred, 

 among others, to sweet-bay, red maple, weeping- 

 willow, etc., as within his own repeated observa- 

 tions growing better out of swamps than in 

 them." He further observes that "plants as a 

 general rule, even those known as water-plants, 

 prefer to grow out of water, except those that 

 grow almost entirely beneath the surface." 



A great many facts are at hand to prove that 

 those plants which are found habitually growing 

 in wet ground may be easily made to grow in 

 dry ground. The Iris versicolor (blue flag), which, 

 in a state of Nature, grows universally in 

 marshes, and keeps perpetual company with 

 Nuphar (pond-lily) and Sagittaria (arrow-head), 

 is a common occupant of the driest gardens. 

 The Lobelia cardinalis (cardinal flower), which I 

 have found below tide-water mark, is also a com- 

 mon garden-flower, and not difficult to cultivate. 



