1. A tissue culture of the endosperm of English rye grass, Lolium perenne L., was established and has been maintained in vitro for more than 21/2 years. The initial outgrowths of tissue were obtained from unripened grains 9-10 days postpollination. 2. The growth rate of this tissue, expressed in percentage increase in dry weight during the first 20 days of culture, was 1563%. Several different media were used; the best growth was obtained with those containing either yeast extract or coconut milk as accessory growth factors. Although the tissue was found to be tolerant of variations in pH value, temperature, and concentrations of yeast extract, coconut milk, and sucrose, the best growth was obtained on media containing 0.25-0.50% yeast extract, 2.0% sucrose, and 1.0 mg/l IAA, at pH 6.1, and 26⚬ C. 3. Attempts were made to culture excised, immature embryos of barley and rye grass on the cultured endosperm. Such cultures proved to be of no discernible benefit to the growth of these embryos. 4. Since the ini...
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