. Contributions from the Laboratory of Plant Genetics. 356 AMERICAN JOURNAL OF BOTANY [Vol. II, In Scilla, the modal length of time required for pollen-germination is about 20 minutes. In a series of 25 pollen grains taken at random, for example, 6, or 24 percent, germinated within 15 minutes after planting, 10 others, or 40 percent of the total, germinated within 20 minutes, 5, or 20 percent, required 25 minutes, and 2, or 8 percent, germinated in 45 minutes: the remaining 2 grains failed to germinate. A potent factor in determining 5000 4 5CC 4000 c c u o E 30OC c 5,2500. c â âºJ 2000 1500:
. Contributions from the Laboratory of Plant Genetics. 356 AMERICAN JOURNAL OF BOTANY [Vol. II, In Scilla, the modal length of time required for pollen-germination is about 20 minutes. In a series of 25 pollen grains taken at random, for example, 6, or 24 percent, germinated within 15 minutes after planting, 10 others, or 40 percent of the total, germinated within 20 minutes, 5, or 20 percent, required 25 minutes, and 2, or 8 percent, germinated in 45 minutes: the remaining 2 grains failed to germinate. A potent factor in determining 5000 4 5CC 4000 c c u o E 30OC c 5,2500. c â âºJ 2000 1500: lOOC. 100- c 0 1 234 5 6789 10 11 Tiae in hours. Text Fig. 2. Growth curves of pollen tubes of Vinca minor grown on an artificial medium consisting of percent agar, 10 percent cane sugar, and a little sterile yeast. The tubes were grown at an oven temperature of 2j°-2S° C. and measured periodically at room temperature, generally slightly lower. the variability in ultimate length of pollen tubes growing in vitro is the bursting of the tubes during elongation. Tubes in any stage of growth may suddenly explode at the tip, and of course cease to grow further. Up to the time of bursting, these tubes can not be distinguished by their beha- vior from those which survive them. In text figure 1, the growth curves are given of three tubes of Scilla, constituting a fair sample of those whose elongation was not terminated by bursting. They were grown on a culture medium consisting of 2 percent agar, 10 percent cane sugar, and a little sterile yeast. While the ultimate length reached by each of the three tubes represented in text figure 1 differs somewhat, and while there is some variability between them in rate of growth, the type of growth curve given by each is essentially the same. It resembles that of a monomolecular autocatalytic reaction where the amount of substrate is limited. The rate is slow at first, then. Please note that these images are extracted from scanned pag
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