Life on the Farm |
Other editions - View all
Common terms and phrases
absorbed absorption Achillea Millefolium agency Agrostis Agrostis vulgaris alluded ammonia salts beans become branches Bromus mollis buds carbonic acid cells cereals changes character chemical chlorophyll circumstances clover constitution contain crops cultivator Darwin death diminished direction effects especially farmer favourable fertilisation Festuca ovina fibre flower fluid formation fruit grain grasses gravitation growing points grown growth heat Holcus lanatus increased influence injury leaf leaves Leguminosa leguminous plants less liquid mangels membrane mentioned ments mineral and ammonia mineral manures miscellaneous plants moisture molecules movements nature nitrate of soda nitrogenous manures oxygen particular Plantago lanceolata Poa pratensis Poa trivialis pollen potash potato pratensis produce proportion protoplasm quantity radicle result ripening root Rothamsted Rumex Acetosa season seed seedling side soil starch stem structure substance superphosphate supply surface takes place temperature tendency tion tissues tree tuber turgescence turnips unmanured plots vapour variety varying vegetation weeds wheat woody
Popular passages
Page 60 - We believe that there is no structure in plants more wonderful, as far as its functions are concerned, than the tip of the radicle. If the tip be lightly pressed or burnt or cut, it transmits an influence to the upper adjoining part, causing it to bend away from the affected side...
Page 61 - It is hardly an exaggeration to say that the tip of the radicle thus endowed, and having the power of directing the movements of the adjoining parts, acts like the brain of one of the lower animals...
Page 61 - ... towards the centre of gravity. In almost every case we can clearly perceive the final purpose or advantage of the several movements. Two or perhaps more of the exciting causes often act simultaneously on the tip, and one conquers the other, no doubt, in accordance with its importance for the life of the plant.
Page 61 - ... in accordance with its importance for the life of the plant. The course pursued by the radicle in penetrating the ground must be determined by the tip ; hence it has acquired such diverse kinds of sensitiveness. It is hardly an exaggeration to say that the tip of the radicle, thus endowed, and having the power...
Page 52 - The growing part does not therefore act like a nail when hammered into a board, but more like a wedge of wood, which, whilst slowly driven into a crevice, continually expands at the same time by the absorption of water ; and a wedge thus acting will split even a mass of rock.
Page 60 - ... more surprising, the tip can distinguish between a slightly harder and softer object, by which it is simultaneously pressed on opposite sides. If, however, the radicle is pressed by a similar object a little above the tip, the pressed part does not transmit any influence to the more distant parts, but bends abruptly towards the object. If the tip perceives the air to be moister on one side than on the other, it likewise transmits the influence to the upper adjoining part, which bends towards...
Page 60 - ... continually moving his head from side to side, or circumnutating, he will feel any stone or other obstacle, as well as any difference in the hardness of the soil, and he will turn from that side. If the earth is damper on one than on the other side, he will turn thither as to better hunting ground.
Page 59 - ... which is perhaps only the indirect result of the radicles being highly sensitive to other stimuli, is of any service to the plant. The direction which the apex takes at each successive period of the growth of a root, ultimately 'determines its whole course ; it is therefore highly important that the apex should pursue from the first the most advantageous direction ; and we can thus understand why sensitiveness to geotropism, to contact and to moisture, all reside in the tip, and why the tip determines...
Page 1 - That he deserves best of his country, who can make two blades of grass grow where only one grew before...
Page 59 - Considering the several facts given in this chapter, we see that the course followed by a root through the soil is governed by extraordinarily complex and diversified agencies, — by geotropism acting in a different manner on the primary, secondary, and tertiary radicles, — by sensitiveness to contact, different in kind in the apex and in the part immediately above the apex, and apparently by sensitiveness to the varying dampness of different parts of the soil. These several stimuli to movement...