AGRICULTURAL BOTANY. L23 



AGRICULTURAL BOTANY. 



The relation of plant physiology to the development of agriculture, A. I •'. 

 Woods (U. S. Dept. Agr. Yearbook 1904, pp. 118 132). The author discusses the 

 relation of plant physiology to the development of agriculture, paying particular 

 attention to it- role in plant breeding, the physiological action of plants in securing 

 their nutrition, nature and causes of plant diseases, etc. 



Regarding* the cause of sap pressure and now in the maple, K. M. Wieg wo 

 (Abs. in Science, n ser., .'i {1906), Vo 15, p. 504). I' is claimed thai various inves- 

 tigators have shown thai the seat of pressure in tin- maple during the Bugar season is 

 in the aerial parts of the tree, principally in the trunk, and pressure is induced by 

 temperature acting as a stimulus. When the temperature passes 2 l C. pressure 

 results, lint a freezing of the tissue is by n<» means necessary. 



The ant I mi- reviews the various theories regarding sap pressure, and concludes thai 

 the only adequate explanation is thai pressure is due to the function of living cells. 



The pith rays seem to be the only ones in proper position in the w 1 to allow the 



production of pressure. In this case pressure would be due to the unequal permea- 

 bility, in opposite directions, of the membrane at the ends of the cells. This would 

 quite likely be caused 1>\ the penetration of the morning temperature. Water would 

 tend to pass from the inner layers to the outer, and the sugar carried in solution 

 would be excreted as a necessary factor in the production of pressure. 



Further studies on the starch grain, II. Kraemeb (Abs. in Science, n. ser., 21 

 (1905), No. 5S5, p. 504). — The author calls attention to the alteration of the com- 

 pound starch grains in seeds of Theobroma cacao on the application of heat. Heal 

 was found to transform the starch of cacao into masses resembling the natural starch 

 grains of corn, wheat, rye. barley, and potato in size and shape, and in some cases 

 even showing the concentric or excentric lamellated structures characteristic of those 

 grains. 



Note- are also given on the polariscopic examination of starch grains of differenl 

 origin, in which it was found thai in using a red and green selenite plate the yellow 

 and blue areas of the starch grain did nol occupy the same relative position in all of 

 the grains. Different explanations are offered for this phenomenon, it being attrib- 

 uted to differences in shape and structure of the individual grains, difference in com- 

 position of the different parts of the same grain, or that there are two distinct kinds 

 ..f reserve starch grains. This last hypothesis is believed to be the most plausible. 



Further observations on the nature of color in plants, II. Kkakmkk i Abs. in 

 Science, n. ser. y 21 (1905), No. 5S5, i>/>. 499, 500). — A preliminary account of the 

 author's studies on the nature of color in plants has been given i K. S. R., 16, p. 540 I. 



In the present paper the author summarizes his observations, claiming that plant 

 color substances may he divided into l' classes: ( Organized color principles, which are 

 characterized by being an organic part of the plastid body and insoluble in water or 

 dilute alcohol, but soluble in xylol and similar solvent.-, and unorganized color prin- 

 ciples, which are not a fundamental or organic part of the plastid. hut occur in the 

 vacuoles in the cells of the higher plants and in the vacuolules of the plastids of the 

 brown and red seaweeds. Unorganized color principles are soluble in water and 

 dilute alcohol and insoluble in xylol and similar solvents. 



In the photosynthetic processes of the plant- the unorganized color substances may 

 he produced, a- in the early spring foliage, autumn foliage, foliage of alpine plants, 

 brown and red marine algae, and the foliage of certain varieties of rose.-, beech, nas- 

 turtium, etc. 



The unorganized color substances are distributed ususally al the terminus of the 

 branch, as in the foliage and flowers, or in the rout-; but sometimes they occur in 

 both tops and roots. The wide distribution of so-called flower color substances in 

 other parts of the plant points to the conclusion that they are products of plastid 



