SUMMER TREATMENT OF GREEN-HOUSE PLANTS. 



159 



difference of eleven degrees, which I ac- 

 counted for by the retention of moisture in 

 the black soil. At the same time, the 

 lower stratum of air was 91°; nearly as 

 hot as the black soil. In a number of sub- 

 sequent trials, I have never found the mer- 

 cury to rise above 9CP in the black, and 

 101° in the sandy soil. On the day above 

 mentioned, the water in two different wells 

 in the garden stood respectively at 50^ and 

 56°. I have known the water of deep 

 wells even colder than this ; yet, regularly 

 supplied to thirsty plants after a hot day. 

 This has much the same effect upon plants 

 as drinking excessively of cold water has 

 upon the animal system. 



The flaccid appearance of plants in a hot 

 day evidently shows that the evaporation 

 from them by their leaves, is too great for 

 the supply of moisture they draw from the 

 earth by their roots. The vital energies of 

 the plants are virtually suspended. To 

 speak analogically, the plants are in the 

 hot, dry paroxysm of a fever ; and the ab- 

 sorption of a liquid 50 degrees below the 

 temperature of its own fluids is, to say the 

 least, of very doubtful propriety, and in 

 violation of any law with which physiology 

 has yet made us acquainted. Thirsty plants 

 possess the power of absorbing moisture 

 almost as soon as it is placed within reach 

 of their roots or leaves. In some plants, 

 that are translucent, the ascent of a coloured 

 fluid is immediately perceptible. As much 

 of the fluid is absorbed as the plant is capa- 

 ble of suspending for the time into its vas- 

 cular system, whether the fluid so absorbed 

 be nutritious or deleterious to its vital ex- 

 istence. 



I have digressed thus far from my text, 

 for the purpose of illustrating more plainly 

 the physical relations which various soils 

 and water have to each other; for unless 

 we know how these bear upon each other 



in the open garden, it is impossible that 

 we can succeed in any systematic course 

 of cultivation in pots ; for although we 

 have more control over them, they are also 

 more dependant upon our care and wisdom 

 for the essentials of their existence. Plants 

 kept in a green-house during summer, may 

 be watered any time of the day. I prefer 

 watering about noon. But the water should 

 be exposed to the atmosphere for a few 

 hours before it is used. The plants, of 

 course, must be thoroughly shaded by a 

 rolling blind. But I prefer the early part 

 of the morning for all plants that are not in 

 the house. About this time, the earth and 

 the atmosphere are beginning to lose the 

 moisture they received by condensation the 

 previous night ; and as the leaves absorb 

 moisture generally by their under surface, 

 we thus supply them with it, by the exha- 

 lations of this water during the day ; and 

 thus we are in some measure able to modify 

 the excessive changes of temperature which, 

 in my bumble opinion, is one of the great- 

 est ills to which vegetation is heir, and 

 which has heen abundantly exemplified in 

 the spring that is past. 



The subject of watering is one of the 

 greatest importance, and ought to be duly 

 and deeply considered by practical men. 

 The mind of a gardener must be continu- 

 ally active, to be successful in his pursuits ; 

 and none, however extensive or limited his 

 charge, can exempt himself from mental 

 as well as physical exertion. In our pro- 

 fession, the mind is truly the standard of 

 the man. And as we advance in mental 

 culture, we unconsciously discover that the 

 " power of knowledge' 1 is not a mere figure 

 of speech, nor an empty sound. It makes 

 difficulties disappear, which before seemed 

 unsurmountable ; and it enables us to show 

 that the crude elements of a working man's 

 nature are as susceptible of arrangement, 



