272 BOTANICAL GAZETTE [march 



Osmotic pressure in the potato. — In an effort to throw some light on the 

 physiological basis of tip-burn, Lutman 7 has studied the osmotic pressure of 

 the potato plant throughout a growing season. In the young plant, when the 

 foliage is being formed, the osmotic pressure of the leaves is greater than that 

 of the stems. After the flower buds are formed and the tubers begin to grow, 

 the stalks predominate over the leaves in osmotic pressure. Sugars account 

 for the high pressures of the stalks. Tip-burn begins to appear at this stage, 

 This higher osmotic pressure of the stalks is maintained during the hot weather 

 of July and August. With the coming of cool rainy weather in September 

 and the resumption of growth of the foliage, the leaves again gain the ascend- 

 ancy. As the plant dies the osmotic pressure decreases, the soluble materials 

 being largely transported to the tubers. The osmotic pressure of the growing 

 tubers is always lower than that of the stems and leaves, although above that 

 of the roots. The study does not explain tip-burn, although the author sees 

 two possible explanations of it: (1) the loss of water from the leaves to the 

 stems, due to the higher osmotic pressure of the latter; and (2) the lack of 

 nourishment of the leaves, due to the translocation of food materials from the 

 leaves to the tubers. The author draws some other theoretical and practical 

 conclusions from his data.— S. V. Eaton. 



Anatomy of prairie plants. — Selecting the dominant species from some 

 prairie associations, Miss Hayden 8 has studied their leaf structure and pre- 

 sented considerable data, the most valuable being in the form of plates from 

 drawings of cross-sections. She concludes that prairie plants show a xerophytic 

 tendency in their leaf structure in the form of specialized palisade tissue, thick- 

 walled epidermis, the presence of water-storing tissue, and sometimes of 

 trichomes. 



In studying the subterranean parts of plants from the same habitats, 

 including a larger number from swampy areas, the same author 9 again presents 

 many data in the form of drawings. Her principal conclusions are that in a 

 dry habitat there is a tendency to the production of prominent mechanical 

 tissue and reduction of parenchymatous tissue. In moist habitats, however, 

 parenchymatous tissue is well developed and aerenchyma is abundant in swamp 

 plants. The subterranean stem is predominant in moist lowland regions, and 

 is more efficient than roots in propagation.— Geo. D. Fuller. 



* LUTMAN, B. F., Osmotic pressures in the potato plant at various stages of 

 growth. Amer, Jour. Bot. 6:181-202. fiw. 2. 1010. 



Ada 



• • 



in central Iowa. Amer. Jour. Bot. 6:69-85. pis. 10-14. 1919. 



, The ecological subterranean anatomy of some plants of a prairie province 



in central Iowa. Amer. Jour. Bot. 6:87-105. pis. 15-28. 1919. 



