1922] ROBBINS—ROOT TIPS AND STEM TIPS 389 
3. The excised root tips of peas, corn, and cotton make little 
growth in the dark in solution cultures containing mineral salts and 
lacking carbohydrate. 
4. The growth of the isolated root tips of peas, corn, and cotton 
is markedly greater in solution cultures containing glucose than in 
those containing levulose. 
5. The excised roots of corn respond normally to gravity when 
grown on agar containing mineral salts and glucose. 
6. The isolated shoot tips of peas and corn make considerable 
growth in the dark in sterile solution cultures containing mineral 
salts and glucose or levulose, but little in the absence of carbo- 
hydrates. 
7- The excised shoot tips of corn and peas grown in sugar 
solutions remain chlorotic, and those of peas show the stem elonga- 
tion and small leaf development characteristic of plants grown in 
the dark. 
8. When the excised root tips of corn are grown for ten days or 
two weeks in the dark in a solution culture containing glucose and 
mineral salts, and the tip is then cut off and transferred to a fresh 
solution of the same type, the amount of growth in the second 
period is less than that in the first, and ceases in the third period. 
UNIVERSITY oF Missouri 
CoLumsia, Mo. 
LITERATURE CITED 
1. ANDREWS, F. M., and Beats, C. C., The effect of soaking in water and 
aeration on the growth of Zea Mays. Bull. Torr. Bot. Club 46:91-100. 
IgIg 
- ANDRONEsCU, Demetrius Ion, Germination and further development of 
embryo of Zea Mays separated from the endosperm. Amer. Jour. Bot. 
6:443-452. IQIQ. 
Buckner, G. D., and Kastte, J. H., The growth of isolated embryos. 
Jour. Biol. Chem. 29:209-213. 1917. 
- Brannon, J. M., A simple method for growing plants. Amer. Jour. Bot. 
8:176-178. 1912. 
HaBeRLannt, G., C I isolierten Pf llen, Sitzungsb. 
Akad. Wiss. Wien. Math.-Natur Classe. 111B:69-92. 1902. 
iS) 
ff 
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