THE BATTLE OF LIFE AMONG PLANTS. 79 



tion, when some accident has interfered with the previously-existing 

 conditions. When woods are cut down, when soil from a depth is 

 laid on the surface, when extensive fires occur, when lakes are 

 drained; in fact, when any sudden alteration takes place in external 

 circumstances, then we may expect to find a corresponding change in 

 the vegetation. One set of plants profits by the change, another 

 suffers. It may be asked, " Where do the new arrivals come from ? " 

 Sometimes, no doubt, the seeds are wafted from a distance, and, find- 

 ing a suitable abiding-place, germinate. This is, perhaps, more espe- 

 cially the case with the spores of fungi, whose extreme minuteness 

 favors their dispersion in this way. But it often happens that the 

 facts of the case will not admit of such an interpretation, and then we 

 can only fall back on the supposition that the seeds or bulbs existed in 

 the soil, but under circumstances not favorable to their development. 



The ground in this way is looked on by Alphonse de Candolle and 

 Darwin as a vast magazine of seeds, etc., capable of retaining their 

 vitality for a more or loss prolonged period, according to circum- 

 stances, and ready to avail themselves of any change that may be 

 beneficial to them. That this is so in some places has been proved by 

 results, but it seems equally clear that this does not hold good in all 

 places. Allusion has already been made to the apparently capricious 

 appearance of our British orchids. The downs or the fields that in 

 one summer yielded abundance of bee, of fly, or of spider orchids, 

 may, in another year, scarcely furnish a single one. The explanation 

 of this peculiarity lies in the special organization of the plant, well 

 described by Prillieux and other botanists, from whose observations 

 it appears that the plants in question naturally pass through several 

 stages, which, for our present purpose, it is not necessary to detail, 

 and these stages may be prolonged according to circumstances. The 

 flowering stage is thus arrived at in one season, while in another all 

 the energies of the plant may be taken up in forming tubers and 

 leaves. A very remarkable instance of the fact just alluded to was 

 communicated to the writer by a competent observer, Mr. George 

 Oxenden, of Broom Park, Kent. This gentleman had been acquainted 

 with a particular field for some forty years, during which time it had 

 been under the plough, but at the expiration of this period it was laid 

 down in grass, when the very next year a profusion of bee-orchids was 

 observed in it. In this case the time was too short for seeds to have 

 germinated and to have progi-essed to the flowering state. There 

 seems no other solution than that the tubers must have been in the 

 ground some time previously, but that, from the ploughing and 

 cropping of the soil, they had not had a fair chsnce of developing 

 flowers. 



The facts we have mentioned are, in the main, intelligible enough. 

 We can see the why and the wherefore without much difficulty ; but 

 it is not so always. For instance, it is difficult to account for the sig- 



