12 Hints on Vegetation. 



acids, or by lime. In regard to the myriads of insects with which the 

 air abounds, it is more difficult to point out a remedy. It is said, 

 that in some parts of the Continent, they surround their gardens with 

 a broad row, or belt of hemp, the smell of which is particularly nox- 

 ious to insects *. Sometimes the depredations of vermin are occasioned 

 by the weakness of the plant, and the poverty of the soil in which it 

 grows ; for insects are more apt to attack a weakly, than a vigorous 

 plant. This is supposed to have been the case in regard to the ce- 

 lebrated Hessian fly of America, which originated from bad culture 

 during the war, in consequence of which the wheat became stunted 

 and diseased. The mischief vanished with good cultivation ; and in- 

 deed it is asserted, that fields, properly manured, were never affected 

 by it, though in the immediate neighbourhood of those which were. 



3. On the Means of raising new Varieties of Plants and 

 Vegetables. 



It has long been known, by those who have studied the theory of 

 vegetation, that by applying the pollen from the stamens of one spe- 

 cies of tree or plant, to the pistil of another of the same sort, the 

 seeds which result from this cross impregnation, produce new varie- 

 ties. For instance, by thus admixing the farina of two different varie- 

 ties of the potatoe, when in flower, new varieties are produced, where- 

 as it is ascertained, that no alteration in the plan of cultivating the 

 potatoes themselves, or any change of soil, ever can have that effect. 

 The same system furnishes the only means by which the production 

 of new kinds of apples, and fruits, can be obtained ; for let any sort 

 of fruit tree be propagated, in whatever numbers, by engrafting or 

 budding, and on whatever stocks, or by whatever other means, it 

 will create no new variety in the fruit. The change takes place in the 

 seed, and can only be discovered in the next generation. There can 

 be no doubt therefore, that by great attention, and skilful management 

 in crossing the pollen of species, important changes may be produced, 

 in the habits and general properties of vegetables or of fruits, as well as 

 in animals, and that new varieties, of great value, maybe procured f. 



Conclusion. 



These cursory hints have been sketched out, for the purpose of giving 

 some general idea of the principles of vegetation, and the means of 

 promoting the growth of plants, and of preventing those injuries to 

 which they are liable. 



* The celebrated Bergman prevented the Phalcena brumata, laying its nox- 

 ious eggs in the buds of blossoms, by tying the tarred bark of a birch round 

 the stem of fruit trees. See Thunbergs Travels, vol. iv. p. 285. 



f This intricate subject is very fully explained in Dr Darwin's Phytologia, 

 Sect. 7, " On the Organs of Reproduction of Vegetables." Mr Knight of 

 Downton, in Herefordshire, the distinguished President of the London Hor- 

 ticultural Society, has likewise discussed this subject with his usual ability ; and 

 we are much indebted to Mr Neill, Secretary to the Caledonian Horticultural 

 Society, for the useful information he has given regarding it. See Memoirs 

 of that Society, No. 10. p. 219. 



