HORTICULTUARAL JOURNAL. 267 



SOME PRINCIPLES OF VEGETABLE PHYSIOLOGY BEARING 

 ON THE CULTURE OF PLANTS. 



BY PROFESSOR W. H. DE VRIESE, OF THE UNIVERSITY OF LEYDEN.. 

 (Traaslated from the Dutch.) 



If we consider the vegetable kingdom attentively, we are astonished as 

 much with the variety as with the greatness and magnificence of the phe- 

 nomena which it offers to our contemplation. Almost every season, every 

 day, every hour, and every place, presents us plants under different circum- 

 stances, with peculiar qualities and in varied forms. Scarcely does the soft 

 air of spring refresh the earth, when every object, in which there is still a 

 germ of life, becomes developed with astonishing rapidity. The plants 

 which spring has graced with foliage, summer decks with a multitude of 

 flowers. In autumn the fruits are collected. In winter those plants, once 

 so beautiful, are found to be, some in a state of dissolution, others in a state 

 of rest,' or in a continued development, which proves that nature is engaged 

 in an indefatigable activity. But, in' winter, the greater number of plants 

 die; the fallen foliage decomposes, returns into the earth, and becomes the 

 rich source of nutriment for a succeeding growth. 



But to judge of those changes which are observed in plants such long pe- 

 riods are not required. How great is the variety in the phenomena of flow- 

 ers and plants daily to be seen ! Observe them attentively early in the 

 morning of June or July, when night has scarcely raised its dark veil, and 

 when the sun is hardly risen above the horizon. Everything has another 

 aspect than during the day. The flowers are closed, the leaves have chang- 

 ed their direction ; those that were spread out seem disposed to close, and 

 present quite another appearance than by day ; you would even think them 

 about to reunite into their former state of buds, and to return to a state of 

 formation and development. The vegetable kingdom sleeps ! However, not 

 only the form and position, but also the colors, have quite a different appear- 

 ance. The fields have often a green color, like that of the waves of the 

 ocean. And this is not only the effect of vapors fallen from the atmosphere, 

 but also of the fact that plants, by their altered directions offer us surfaces 

 that are differently colored. 



Another cause of this phenomenon is that on their surface a cover like 

 wax is left, which the sunbeams cause to disappear afterwards, and then the 

 original color presents itself again. At mid-day all is in its full splendor. 

 The flowers are opened, the leaves are spread out, and often they reflect the 

 sunbeams from their shining surfaces ; sweet smells spread over the fields ; 



