204 COLLINS AND KEMPTON : A FIELD AUXANOMETER 



diameter, composed of a few smooth ovoid carpels 8 mm. by 6 mm. in 

 size, borne on the indurated receptacle. Seeds oval, 7 mm. long, 5 mm. 

 in diameter, light yellow, smooth. 



Type in the Berlin Botanical Museum, collected in the state of Piauhy, 

 Brazil, in 1840, by George Gardner (No. 2033). 



Fries compares the leaves of this species to those of Rollinia longifolia, 

 which, however, are relatively narrower and are not rounded at the 

 apex. He says that the flowers and fruit are more like those of Rol- 

 linia emarginata, but specimens of the latter in the U. S. National 

 Herbarium show its fruit to be a solid syncarpium. To this species he 

 assigns as a variety, angustifolia, a plant in the Berlin Botanical Museum 

 collected at Rio de Janeiro by Glaziou, No. 13508, but of this he figures 

 only a single leaf and gives no account of the flower or fruit. In his 

 figure of the type 6 the wings of the corolla are shown as different from 

 those of Rolliniopsis discreta in size and form, and the mature carpels 

 as ovoid instead of pyriform as in the latter species; moreover he de- 

 scribes R. leptopetala as a tree or shrub with "ramulis, petiolis, pedun- 

 culisque fulvo-tomentosis" . ... and its "jungsten Sprosse 

 von abstehenden gelblichen Haaren wollig." These characters readily 

 serve to disinguish his species from both R. discreta and R. simiarum, 

 as well as from the ferruginous-tomentose R. parvifolia. 



PLANT PHYSIOLOGY.— A field auxanometer. G. N. Collins 

 and J. H. Kempton, Bureau of Plant Industry. 



In studying the effect of different environmental factors, such 

 as light, temperature, and water supply, on the rate of growth 

 of maize varieties, the lack of some means of measuring the 

 elongation of plants growing naturally in the field has for several 

 years been recognized as a serious obstacle. There are two prin- 

 cipal requirements in securing satisfactory measurements: (1) In 

 order to ascribe any observed difference in the behavior of two 

 varieties to its environmental cause it is necessary to make the 

 measurements at short intervals; (2) that due allowance may be 

 made for individual diversity, it is essential to make simultaneous 

 measurements of a number of plants. These conditions have 

 been met by devising a form of auxanometer well adapted to 



* Op. cit. pi. 7, f. 3, 4. 



