462 



SCIENCE 



[N. 8. Vol. XXXVII. No. 951 



such attempts have not been very successful, inas- 

 much as many of the plants have failed to mature 

 seed. Observations were made to ascertain the 

 cause of this. In order to make the subject 

 readily comprehensible attention was invited to 

 the surprising responsiveness of the beet to en- 

 vironment; the responses may be grouped as 

 follows : 



1. The wild beet, a winter annual, ripening and 

 dropping its seed early in autumn. The seed ger- 

 minates before winter sets in, consequently the 

 young seedlings are for many weeks exposed to a 

 comparatively low mean temperature. In early 

 spring — coincident with rising temperatures — the 

 seed stem is put forth, the paucity of foliage 

 being conspicuous. 



2. The wild annual brought into cultivation soon 

 assumes the biennial habit ; its growth being in 

 every known way stimulated from the sowing of 

 seed onwards; planting is carefully planned so 

 that the young seedling shall escape protracted 

 perio4s of low temperature. In response, the 

 roots become storehouses and fail to develop re- 

 productive parts. 



3. The cultivated beet, a biennial, not alone 

 through selection, but more especially because its 

 environments are entirely changed; it is withheld 

 from those periods of restrained growth seen to 

 operate upon the wild beet in its native habitat; 

 instead, its growth is stimulated. 



4. The cultivated beet reverts to the annual 

 habit, whenever it is exposed in the seedling stage 

 to conditions more or less identical with those of 

 the wild beet at the same stage of growth. 



5. Even when the beet is planted out the second 

 spring for the production of seed, there are occa- 

 sions and localities which cause in those beets a 

 greater or less tendency toward non-seeding, 

 ranging from almost normal seed production to 

 absolute foliage conditions. 



6. When placed under conditions where growth 

 stimulus is great and constant, as in a well- 

 heated greenhouse, the cultivated beet becomes 

 perennial in habit, producing, year after year, 

 nothing but foliage. 



Mr. Shaw sought in these varied manifestations 

 a common factor, or group of factors, which act- 

 ing at a critical period in the life of the plant, 

 might be found to control the manner of its devel- 

 opment. Experiments were carried on in Utah 

 during 1912 to determine, if possible, the nature 

 of the conditions responsible for the variations 

 mentioned. 



It was discovered that the condition absolutely 

 necessary for the perfect development of the re- 

 productive parts is a period of restrained growth 

 in the bud rudiments of seedlings, or the buds in 

 the crown of so-called mother beets. While in gen- 

 eral this condition is brought about by low tem- 

 peratures (a mean temperature of 38 to 45° F. 

 apparently being required for the sugar beet) 

 when prevailing for several weeks, the necessary 

 degree of growth inhibition may be brought about 

 by other factors, such as pathological conditions, 

 drouth, starvation. The withdrawal of such a 

 period of inhibited metabolism, according to de- 

 gree, will result in the greater or less degree of 

 approach to foliage conditions, as opposed to the 

 development of reproductive parts. 



Thus, by a study of climatic conditions, suit- 

 able locations where the production of seed may 

 be assured, can be selected with a considerable 

 degree of certainty. The proper time to plant the 

 mother-beets can also be indicated, so that we 

 may be reasonably certain that the beets will pro- 

 duce seed. 



This necessity for a period of inhibited metab- 

 olism, and the fact that it may be brought about 

 by the conditions mentioned, may explain the 

 remarkable inflorescence of moribund fruit trees, 

 or of trees that have been girdled, also the ab- 

 normal behavior of plants carried from a cool to 

 a warm climate. c. L. Shear, 



Corresponding Secretary 



PHILOSOPHICAL SOCIETY, UNIVERSITY OF VIRGINIA 

 MATHEMATICAL AND SCIENTIFIC SECTION 



The fifth meeting of the session of 1912-13 of 

 the Mathematical and Scientific Section was held 

 February 17. 



Professor W. H. Echols read a paper entitled 

 ' ' The Evolutionary Construction of the Imaginary 

 Power of a Number and Its Expression as the 

 Exponential Function. ' ' 



Professor Thomas L. Watson read a paper by 

 himself and Professor Stephen Taber on ' ' Mag- 

 matie Names Proposed in the Quantitative System 

 of Classification for some New Eock Types ia 

 Virginia. ' ' 



Professor Watson presented a second paper by 

 himself and Mr. Justus H. Cline. The subject of 

 this second paper was ' ' Petrology of a Series of 

 Igneous Dikes in Central Western Virginia. ' ' 

 Wm. a. Kepner, 



Secretary 



University of Virginia 



