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absorbed absorption alcohol amount appear assimilation atmosphere bark become Botanische calcic cambium carbonic acid cell-wall cellulose cent changes chemical chlorophyll chlorophyll granules color coloring-matter containing cork cortex cotyledons crystals cutinized cylinder Darwin dicotyledons dilute dissolved ducts elements embryo epidermis evaporation examined experiments fascicles fibres fibro-vascular bundles film flower germination given glass glycerin grains green growth hairs inches instance iodine layer leaf leaves light liquid lower plants mass matters membrane micella microscope minute moisture monocotyledons movement nearly nitric acid nitrogen nucleus observed organs ovule oxygen parenchyma parenchyma cells petiole Pfeffer plants pollen pollen-grains pollen-tube portion produced protein protoplasm radial radicle rays reagents roots Sachs seedlings seeds shown side soil soluble solution sometimes species specimen starch stem stoma stomata structure substance sugar sulphuric surface temperature thickness thin threads tion tissues tracheids transpiration tube vegetable wall wood wood-cells woody young
Page 417 - 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 ; the brain being seated within the anterior end of the body, receiving impressions from the sense-organs, and directing the several movements.
Page 301 - According to the physical hypothesis now generally received, a gas is represented as consisting of solid and perfectly elastic spherical particles or atoms, which move in all directions, and are animated with different degrees of velocity in different gases.
Page 223 - ... at last. Nor does the change of this colloid appear to stop at that point. For the mineral forms of silicic acid, deposited from water, such as flint, are...
Page 224 - But, on the other hand, their peculiar physical aggregation with the chemical indifference referred to, appears to be required in substances that can intervene in the organic processes of life. The plastic elements of the animal body are found in this class.
Page 223 - Although chemically inert in the ordinary sense, colloids possess a compensating activity of their own, arising out of their physical properties. While the rigidity of the crystalline structure shuts out external impressions, the softness of the gelatinous colloid partakes of fluidity, and enables the colloid to become a medium for liquid diffusion, like water itself.
Page 416 - 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 ; and, what is more surprising, the tip can distinguish between a slightly harder and softer object, by which it is simultaneously pressed on opposite sides.
Page 344 - Mrs. Treat, who cultivated many plants in New Jersey, also informs me that " several leaves caught successively three insects each, but most of them were not able to digest the third fly, but died in the attempt. Five leaves, however, digested each three flies, and closed over the fourth, but died soon after the fourth capture.' Many leaves did not digest even one large insect.
Page 449 - ... of one species by evidence of their common origin, or more commonly are inferred to be so from the observation of a series of intermediate forms which bridge over the differences. Only observation can inform us how much difference is compatible with a common origin. The general result of observation is that plants and animals breed true from generation to generation within certain somewhat indeterminate limits of variation; that those individuals which resemble each other within such limits interbreed...
Page 417 - ... it. But as the growing stem lengthens and rises, the tendril might strike against it and be wound up around it. It never does. If we watch these slender Passion-flowers, which show the revolving so well in a sultry day, we may see, with wonder, that when a tendril, sweeping horizontally, comes round so that its base nears the parent stem rising above it, it stops short, rises stiffly upright, moves on in this position until it passes by the stem, then rapidly comes down again to the horizontal...
Page 324 - Accordingly, on the 17th of August, 1771, I put a sprig of mint into a quantity of air, in which a wax candle had burned out, and found that, on the 27th of the same month, another candle burned perfectly well in it. This experiment I repeated, without the least variation in the event, not less than eight or ten times in the remainder of the summer.