570 PHYSICAL GEOGRAPHY. 



of Professor Graham, of the University of Edinburgh. Previous to the year 1715, no 

 broom grew in the king's park at Stirling ; but in that year a camp was formed there, 

 and the surface of the ground consequently was broken in many places. Wherever it was 

 broken, broom sprang up. The plant was subsequently destroyed; but in 1745, a 

 similar growth appeared after the ground had been again broken for a like purpose. 

 Some time afterwards the park was ploughed up, and the broom became generally spread 

 over it. Some years ago a gentleman planted a garden in Stirlingshire, and as he was 

 about to make a bleaching ground in the neighbourhood, he took from six to nine inches 

 of soil off the surface of the field intended for the purpose, and carried it into his garden, 

 afterwards sowing the field with grass seeds. In the field thus uncovered, seedling 

 broom appeared as thick as the grass which had been sown. Professor Graham con- 

 cludes, that the seeds could not in either case have been supplied by the wind : first, 

 because they are heavy, round, and without wings ; and, secondly, because all the broom 

 seed in the district could not have produced such crops as sprung up. The form of the 

 ground is also such, that no stream of water could have transported them. The seeds 

 must have been in the soil, how long and how imbedded cannot be conjectured. The 

 case is still more striking in the United States, of soil turned up from the depth of many 

 feet immediately yielding a crop of white clover. The occurrence of seeds thus buried 

 in the soil of the earth, may explain the appearance of cryptogamous plants in mines in 

 situations peculiarly inaccessible to the ordinary agents of dispersion ; while the growth 

 of wheat from grains found in the sepulchres of the Egyptian kings,' after an entombment 

 certainly of from three to four thousand years, sufficiently attests the tenacity with which 

 enclosed seeds retain their vitality. 



The adaptation of external nature to the wants of man is finely displayed by the vege- 

 table tribes with which the earth is replenished, which minister in a thousand ways to his 

 existence, health, convenience, and refinement. The reproductive power of some species, 

 especially of the more useful kind, is an obvious instance of bountiful design : but, not- 

 withstanding the evidence of it which the experience of the human race has already 

 acquired, we are far from having had the limi* of the prolific quality developed. The 

 orange displays an extraordinary fecundity. A single tree at St. Michael's has been 

 known to bear 20,000 oranges in a season fit for exportation, those damaged and defective 

 amounting to at least one third more. The tea, sugar, and potato plants, yielding pro- 

 ducts which are necessaries of life to the cultivated nations, are additional examples, with 

 the common grasses which clothe the hills and valleys with their refreshing green, form- 

 ing the pastures upon which innumerable flocks and herds graze by day and repose at 

 night. A single potato from the crop of 1844 was cut into twenty- eight sets, which have 

 yielded a produce of sixty-eight pounds' weight during the present year. In the harvest 

 of 1840, a Cambridge agriculturist gathered from one of his fields some very fine ears of 

 wheat, the proceeds of which filled a common wine glass. This was planted the following 

 autumn, and produced a peck of grain, which was again planted November 3. 1841, and 

 yielded rather more than seven bushels. Upon this being sown November 3. 1842, the 

 yield amounted to upwards of 108 bushels, which, being returned to the soil in the 

 autumn of 1843, produced 1868 bushels. In some of the more fertile parts of the table- 

 land of Mexico the common return of the wheat harvest is from thirty -five to forty grains 

 for one, and it frequently exceeds from seventy to eighty for one. It is not undeserving 

 of notice, that the vegetable productions upon which the sustenance of man mainly 

 depends, have the flavour of their fruits accommodated to his taste, being apart from the 

 pungent and the insipid, so that a sufficient quantity may be consumed without annoy- 

 ance or disgust. Yet, as if to accomplish the law of Providence to the human creature, 

 "In the sweat of thy brow shalt thou eat bread," the cereal and leguminous tribes, 



