1919] DI/TUBAL BOTANY. 427 



during August, L916, would be at the Tucson, Ariz., and the Cannel, CaL, labora- 

 tories, respectively, 588.7 and 74.4. Survival of this species ;ii the latter place 

 i* nut considered probable. 



Determination of wilting, A. L. BAKKX (Hot. f,</r.. 66 (1918), Vo. ..'. pp. 81- 

 lin. figs. 5). — A study of Helianthua annuus, as carried oul during 1915 and 

 1916 with standardized hygrometrlc paper according to methods previously <!«■• 

 scribed (E. S. R., 86, p. 824), is saiil t<» give an accurate knowledge of the in- 

 ternal water relations of the plant. 



The exact wilting poinl occurs when there Is a serious rupture of the water 

 columns. The maximum is attained at a time previous i" the great) -i evapora- 

 tion. During the time of approximately maximum evaporation, a marked fall 

 occurs in the index of foliar transpiring power, followed soon by a rise. The 

 ratio between maximum and minimum is not sufficiently definite for the expres 

 sion of a law. A ratio approximating unity marks a state of intense incipient 

 drying. 



When the maximum does not rise ahove the usual minimum, the plant is near 

 its wilting coefficient. High evaporation coincides with high transpiration value, 

 hut during wilting the Index of foliar transpiring power becomes independent of 

 evaporation. A condition of equilibrium is noted to occur during the process of 

 wilting, the duration of this condition supposedly giving a measure of the com- 

 parative drought resistance of different plants. In //. unnuus the equilibrium 

 period for 1915 was much shorter than that for 1910, when the season was much 

 drier. Permanent wilting occurs much sooner in old than in young leaves. 

 Stomatal movements or changes are not important factors when tin' plant is in 

 an intense state of wilting. 



Fertility in Cichorium intybus: Self-compatibility and self-incompatibility 

 among the offspring of self-fertile lines of descent, A. B. Stovt (.Jour. QetU t- 

 iis. 7 (/.''/.si. No. .>. pp. 11-10.]. pis. 8).— This work continues, with material 

 Identical in part, thai previously noted and is also related to some winch have 



been reported more recently (E. S. R., 39, p. -132; 40, p. 225). 



The results presented in the present paper pertain to the variation, the 

 heredity, and the results of selection in respect to seed production in progenies 

 of seif-feriile plaids oi chicory, these having first appeai'ed sporadically among 

 the descendants of self-sterile parents. The type of sterility previously studied 

 lias been ascribed to physiological and not to anatomical incompatibility. 

 Embryo abortion resulting from gametic Incompatibility developing after fertil- 

 ization may, it is thought, also account in part for the decreased seed produc- 

 tion and poor germination. These facts, the many instances of cross-sterility and 

 •elf-Sterility in wild and cultivated varieties, instances where self-fertile plants 

 appear in the progeny of self-Sterile parents, and oilier facts are thought to he 

 of special importance in their bearing on the fundamental problems of sexuality 

 and fertilization, particularly as noted in the hisexua! higher plants. 



The plants for which data are here presented and discussed in considerable 

 detail were descendants during and since 11)1(5 of three self-sterile parents, two 

 of which were of common, unimproved chicory, these being each crossed with a 

 Wild, White-flowered plant so that there resulted two main families with their 

 reciprocals. This work is thought to strengthen the conclusion that self- and 

 cross-incompatibilities in chicory develop independently of anatomical incom- 

 patibility with its marked structural differences and adaptations for cross 

 pollination also independently of embryo abortion, at least of the sort due to 

 malnutrition of embryos. Impotence and embryo abortion probably occur, how- 

 ever, iii chicory. The new data here reported are considered to he in full accord 

 with those previously noted in the several contributions on this Bubject 



