223 



states of moisture vary as much as those of heat and light " : varieties 

 of soil also visibly affect plants : and lastly — 



" All plants require rest, and obtain it in some countries by the rigour of winter ; 

 in others by the scorching and arid heat of summer. Some, " after short slumber 

 wake to life again," while the sleep of others is unbroken for many months. This is 

 the case with most alpine plants, and is necessary to their well-being. * * In 

 Egypt the blue water-lily obtains rest in a curious way. Mr. Traill, the gardener of 

 Ibrahim Pacha, infonned me that this plant abounds in several of the canals at Alex- 

 andria, which at certain seasons become dry ; and the beds of these canals, which 

 quickly become burnt as hard as bricks by the action of the sun, are then used as car- 

 riage-roads. When the water is again admitted the plant resumes its growth with 

 redoubled vigour.'' — p. 5. 



On the power possessed by plants of adapting themselves in a cer- 

 tain degree to the circumstances in which they are placed, the author 

 remarks : — 



" To suit all the varied conditions to which I have thus briefly alluded, and under 

 which plants are found to exist, they have been formed by their Almighty Creator of 

 different structures and constitutions, to fit them for the stations they severally hold 

 in creation ; and so striking are the results, that every different region of the globe is 

 characterized by peculiar forms of vegetation. A practised botanical eye can with 

 certainty, in almost all cases, predict the capabilities of any hitherto unknown coun- 

 try, by an inspection of the plants which it produces. * * But in order to give 

 us a clearer idea of the " strong connexions, nice dependencies," existing between cli- 

 mate and vegetation, let us survey plants in a state of nature. We shall find some 

 restricted to certain situations, while others have a wide range, or greater powers of 

 adaptation. It is not perhaps going too far to assert, that no two plants are alike in 

 this particular, or in other words, that the constitution of every individual plant is dif- 

 ferent. Of the former, Trichomanes speciosum is an example, it not being able to ex- 

 ist, even for a short time, in a dry atmosphere : of the latter, familiar examples are 

 presented to us in the London Pride and the Auricula ; these of course grow in great- 

 er or less luxuriance, as the conditions are more or less favorable.'' — p. 6. 



Chap. II. — On the Causes which interfere with the Growth of 

 Plants in large towns. Among these are more particularly mention- 

 ed " deficiency of light, the dryness of the atmosphere, the fuliginous 

 matter with which the air of large towns is always more or less load- 

 ed, and the evolution of noxious gases from manufactories." The 

 author expresses his belief that the generally depressed state of ve- 

 getation in large towns, is chiefly due to the quantity of soot floating 

 in the atmosphere ; and that although deficiency of light and mois- 

 ture certainly exerts an influence to a certain extent, yet that neither 

 of these, nor the evolution of noxious gases, nor the three combined, 

 is the sole or even the chief enemy to the growth of plants in 

 a town atmosphere. After quoting from Mr. Ellis's paper in the 



