. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. 42 THE VEGETABLE CELL IN GENERAL. exterior a delicate film. Mej-er believes that the coloring matter takes the form of grains of extreme minuteness which are inter- spersed through the whole substance, wliile Tschireli holds that the pigment, dissolved in a liquid similar to the ethereal oils, is diffused through the mass. 171. If starch is present in large amount in chloroplastids, iodine causes at once a deep bluish-brown color ; but if the starch is not very
. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. 42 THE VEGETABLE CELL IN GENERAL. exterior a delicate film. Mej-er believes that the coloring matter takes the form of grains of extreme minuteness which are inter- spersed through the whole substance, wliile Tschireli holds that the pigment, dissolved in a liquid similar to the ethereal oils, is diffused through the mass. 171. If starch is present in large amount in chloroplastids, iodine causes at once a deep bluish-brown color ; but if the starch is not very abundant, the characteristic blue reaction is concealed by the yellow produced by the protein reaction of the protoplasm. Hence it is well, after having removed the chlorophyll pigment by alcohol and subsequent washing with water, to treat the speci- men with moderately strong potassic hydrate in order to dissolve the protein matters. If this has been well done, and the speci- men carefully freed from the potash, the protoplasmic mass and its imbedded granules will seem to have completely disappeared ; but the skilful use of oblique illumination will show that an un- dissolved trace of something having the former contours remains behind. Application of iodine brings out minute blue points where the grannies were. Chloral hjdrate of the strength recommended in 53 may replace potassic hydrate in this examination. 172. The starch in chlorophyll granules is sometimes wholly within the granule; but it is occa- sionally— especiallj' in the case of flattened granules — found on their exterior, forming a noticeable pro- tuberance. 173. When a plant containing g chlorophyll gi-anules is kept for a time in darkness, the production of starch is arrested ; and if other forms of activity continue, even that starch which has already accumulated in the granules soon disappears. Furthermore, the color of the grannies is changed fi-om green to yellow ; and if the change is not arrested at
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