. Plant physiology. Plant physiology. INFLUENCE OF EXTERNAL CONDITIONS ON GROWTH 225 ture alone, other conditions being equal, are sufficient to produce differences in the external appearance of certain plants. Thus, for example, the stem of Mimulus tilingii grows vertically upward at ordinary temperatures, while it bends or even assumes a horizontal position at lower temperatures. It is well known that the climate of high mountains is characterized by great fluctuations in temperature, and the question arises whether this environmental feature does not also play a part in producing the peculi
. Plant physiology. Plant physiology. INFLUENCE OF EXTERNAL CONDITIONS ON GROWTH 225 ture alone, other conditions being equal, are sufficient to produce differences in the external appearance of certain plants. Thus, for example, the stem of Mimulus tilingii grows vertically upward at ordinary temperatures, while it bends or even assumes a horizontal position at lower temperatures. It is well known that the climate of high mountains is characterized by great fluctuations in temperature, and the question arises whether this environmental feature does not also play a part in producing the peculiar aspect of alpine plants. To answer this question by experiment, plants from low altitudes were grown from the seed in vessels that were surrounded with ice at night and were exposed to the usual lowland conditions during the day, thus simulating the daily temperature fluctuation observed on high mountains. Plants thus grown possessed the special peculiarities of the forms occurring in alpine floras (limited enlargement, short internodes, small, tough leaves, and early flowering periods). A striking example of the influence of temperature upon plant configuration is found in the case of a species of acetic acid bacterium {Bacterium pasteurianum).. Fig. 103.—Bacterium 'pasteurianum, grown at 34° Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Palladin, Vladimir Ivanovich, 1859-1922; Livingston, Burton Edward, 1875-; Hopping, Aleita, 1890-. Philadelphia, P. Blakiston's Son & Co
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