Miscellaneous Products. 



442 



IMay, 1909. 



When a vegetable product is gathered 

 from plants not under cultivation, the 

 supply, from a variety of causes, must 

 of necessity be fluctuating, and, more- 

 over, the sources of supply are in 

 constant danger of being exhausted, as 

 was the case when cinchona bark was 

 alone obtained from the forests of the 

 Andes. There can be no question, 

 therefore, of the advisability of tropical 

 agriculturists turning their attention to 

 the cultivation of the vegetable ivory 

 plant, as they have already done in the 

 case of other economical trees. The 

 constant increase in consumption of the 

 article points to the success of such an 

 undertaking, . 



In Jamaica, in Trinidad, and in Domi- 

 nica, the plant would thrive along the 

 banks of the rivers and streams which 



run through many of the estates, and 

 thus a profitable crop might be obtained 

 from land which is now principally 

 occupied by scrub or a jungle of reeds. 

 Trees grown at St. Aroment, Dominica, 

 were grown from seed sent from 

 Panama. The seeds germinated readily 

 and the plants were hardy, and they 

 have grown at the edge of a small 

 stream — which sometimes runs dry — 

 without any care or cultivation. In 

 suitable situations, therefore, they can 

 look after themselves, so that, beyond 

 the original small expenditure in raising 

 the plants and setting them out, nothing 

 else is required, and, in these circum- 

 stances, a plantation of ivory-nut palms 

 should be a very profitable property.— 

 West Indian Bulletin, Vol. IX., No. 3, 

 1908. 



HORTICULTURE. 



WATER AND WATERING. 



By J. J. Willis, Harpenden. 



Water is the medium by which the 

 soluble matters of the soil are conveyed 

 through the roots into the interior of 

 plants. 



An important fact in the relation of 

 vegetation to moisture is seen in the 

 effect exerted by the humidity of 

 the atmosphere upon its temperature. 

 Without more or less vapour m the 

 atmosphere, the radiation would cool 

 the surface of the earth so rapidly as 

 to destroy the life of all tender plants. 

 The principal part of the rays of the 

 sun pass through the air, even when 

 it is saturated with moisture, without 

 appreciably heating it; but the heat 

 radiated from the earth and every ob- 

 ject upon it is intercepted and absorbed 

 by the humidity in the air ; the atmos- 

 pheric warmth is, therefore, clearly- 

 related not only to the heat of the sun s 

 rays but also to the moisture of the air. 

 Like the covering of a cold frame, the 

 moist air admits the light rays by day 

 and prevents the exit of the heat to 

 which they give rise at night. Hence 

 the clearest, driest nights are the coldest. 

 Also the driest regions, like the desert 

 of Sahara, have the coldest nights, and 

 the cold of high elevations is due to 

 the same course. 



Professor Tyndall says : T " The re- 

 moval, for a single summer night, of the 

 acqeous vapour from the atmosphere 

 that covers England would be attended 



by the destruction of every plant which 

 a freezing temperature would kill." 

 Humidity and temperature are, there- 

 fore, intimately connected. 



Although the heat of the sun causes 

 evaporation from plants, its amount is 

 governed by the humidity of the air 

 and the velocity of the wind. 



If the gardener could regulate the 

 moisture of the atmosphere surrounding 

 his crops, maintaining the precise condi- 

 tions for keeping up the proper evapor- 

 ation by applying water artificially and 

 only in circumscribed limits to their 

 roots, he could be assured of success. 

 While he may do so in his green-house, 

 there are no means of regulating the 

 heat and moisture of the open air and 

 also of the soil. It is for these reasons 

 that watering outdoor crops in very 

 hot weather is more often productive 

 of harm than of benefit. 



When the earth is naturally mois- 

 tened by rain, the whole air is satur- 

 ated with moisture, preventing both a 

 too rapid transpiration from the leaves 

 and an uudue evaporation from, and 

 consequent chilling of, the soil. If 

 watering is done at all, it should be in 

 cloudy weather ; but it is most frequent- 

 ly injudiciously practised in dry, hot 

 weather, and so circumscribed in extent 

 that it can have little or no effect upon 

 the atmosphere. The roots are tempo- 

 rarily excited, and the dry, hot air robs 

 the plants of the moisture through the 

 leaves as rapidly as it can be supplied 

 by the roots. 



