88 DR. V. MARTIUS 



There are deviations which will have to be ascribed to the 

 jDrevalent direction of winds, or thunder storros, the peculiarities of 

 seasons, sources of irrigation, the physical and chemical qualities 

 of the soil, &c. But there will still remain phenomena which 

 admit of no satisfactory solution ; as, for instance, the torsion 

 of trunks, especially of Conifers, producing a corresponding 

 structure in the wood, the fibres turning with (that is, from right 

 to left), or contrary to (from left to right), the course of the sun 

 [nachsonniges nnd widersonniyes Holz), and which varieties are 

 practically attended to in the highlands of Bavaria. 



I feel convinced, that our plant-houses ought to be constructed 

 in accordance with the preceding considerations, the chief results 

 of which are — 1, that each tree possesses, originally, the con- 

 ditions of uniform and symmetrical development ; 2, that a 

 variety of external influences interferes with that development ; 

 and 3, these influences, though they may degenerate into cases of 

 sickness, are by no means to be looked upon as unnatural, but 

 belong to the ordinary system of nature in the vegetable creation, 

 constituting what the ingenious Kielmeyer calls Politia verjeta- 

 biliiun. Hence this twofold corollary ; the number of plants in a 

 house must be judiciously limited, and partial developments will 

 sometimes occur among the plants contained in it, since nature 

 allows such to exist in the wild state. In England, where 

 numerous establishments of this sort exist, and on a large scale, 

 such overcrowdings are rarely seen ; and besides, cultivators 

 frequently limit their efforts to particular objects. Not so in 

 Germany, where the contrary tendency prevails, and a stranger 

 consequently forms an unfavourable opinion of our so-called 

 riches, especially in public gardens. Again, inexperienced, only 

 half-informed people, are apt to blame the cultivator, when he sees 

 that plants in a hot-house strive to elongate themselves towards 

 the light, although he would hardly notice the much more 

 frequent and still stronger tendency of that description in open 

 nature. Excess may of course be the result of a faulty con- 

 struction of the building, and become offensive to the eye ; but 

 my experience has taught me, that so far from the turning of a 

 woody plant towards the light being injurious to their production 

 of flowers, it has occurred most frequently in years which were 

 the most prolific in flowers. I conclude that both these 

 events resulted from one source, namely, a favourable com- 

 bination of circumstances, causing a higher degree of vegetable 

 activity. 



