No. 2, Septembeu, 1921] PHYSIOLOGY 163 



is the ratio of the growth increment to the absolute size of the individual at a given stage. 

 Three problems were under consideration, namely: (1) The correlation between the absolute 

 size of an organism at its several periods of development; (2) the correlation between the 

 growth increments of the organism during the several growth periods; (3) the correlation be- 

 tween the absolute size of the organism at given stages of development and subsequent growth 

 increments. A discussion of each problem follows. Helianthus plants were used for study. 

 The general results show that the actual size of an individual at any stage of development is 

 closely correlated with its size at other closely correlated stages of development but rapidly 

 diminishes as the growth stages become widely separated. Also the ultimate size of an organ- 

 ism is onlj' slightly determined by its initial size. The correlation between successive growth 

 increments is positive in sign and has the general average of .501. The correlation for incre- 

 ments of weekly periods separated by an interval of 1 week is about .225. The correlation 

 between growth increments more widely separated is on the average negative in sign. Plants 

 which grow rapidlj'' during a certain stage of development will grow more rapidly during a 

 closely associated period, but widely separated periods have little or no relationship between 

 the growth increments. The growth increment is positively correlated with its size at an im- 

 mediately preceding stage. In the early stages the growth increments of 2 or 3 subsequent 

 periods during the early stages of growth are positively correlated with the initial size of the 

 organism. — T. J. Fitzpatrick. 



1038. Reed, Howard S. Growth and sap concentration. Jour. Agric. Res. 21 : 81-98. 

 7 fig. 1921. — Material for the investigation consisted of walnut (Juglans) and apr cot (Pru- 

 nus armeniaca) trees, both in their 2nd year of growth, and of new shoots of orange {Citrus). — 

 The 2 variables, growth and concentration of sap, vary in opposite directions. As the season 

 advances the concentration of sap increases and, in apricot, continues to increase after 

 active growth ceases. This is largely a matter of the accumulation of solutes, although 

 diminished absorption of water may be responsible in part. Addition of water to the soil 

 usually results in a diminution of sap concentration. This is the only one of the external 

 factors considered that seems to affect concentration. Sap concentration of shoots on heavily 

 pruned trees is lower than that of shoots from unpruned trees. A concentration gradient 

 exists in the shoots, the concentration of sap at the t ps being greater than at the base of 

 shoots. Low concentrations of sap in the shoot as a whole appear o be associated with 

 abundant water intake and rapid vegetative growth, while higher concentrations are associa- 

 ted with slow growth and fruit-bud formation. Summer pruning of fruit trees is not only 

 unnecessary but may be detrimental. — D. Reddick. 



1039. ScHtJEPP, Otto. tJber Form und Darstellung der Wachstimiskurven. [The form 

 and representation of growth curves.] Ber. Deutsch. Bot. Ges. 38: 193-199. 1920. 



MOVEMENTS OF GROWTH AND TURGOR CHANGES 



1040. Oehlkers, Friedrich. Zur reizphysiologischen Analyse der post-fioralenKriimmun- 

 gen des Bliitenstiels von Tropaeolum majus. [An analysis of the post-floral curvatures of the 

 peduncle of Tropaeolum majus.] Ber. Deutsch. Bot. Ges. 38: 79-S3. 1920. — This is a pre- 

 liminary report. The curvatures in question begin about 12 hours after the pollination of 

 the protandrous flowers. First, the apical zone of the peduncle, beginning just below the 

 ovary, bends through about 90°. The second curvature, in a 3-5 cm. zone, below the region 

 of the first curvature, occurs within the next 24 hours; and this curvature may amount to as 

 much as 270°, generally lessened somewhat by a slight counter reaction. Finally, about the 

 time of the ripening of the seeds, a short zone at the base and in the axil of the subtending 

 leaf curves in the same direction as the above. By e.xperiments with peduncles detached 

 from the plant and subjected to unilateral illumination, by rotation upon the clinostat, 

 and by retention in the dark room, the author has attempted to find an explanation for the 

 first 2 curvatures and for the variations which sometimes occur in the reactions of plants 

 growing outdoors. His principal conclusions are that the post-floral curvatures represent 

 a combined sensitive reaction which can be accounted for only on the basis of a change of 



