1919] AGRICULTURAL, BOTANY. 225 



obtained, with a discussion, generalizing the facts observed in the form of the 

 law that equal masses of leaves produce equal masses of shoots regardless of 

 the number of the latter. 



Experiments testing the validity of this law for the regeneration of shoots 

 on isolated stems showed that the mass of the shoots regenerated on two sets 

 of stems (split longitudinally in halves) was in exact proportion to that of the 

 attached leaves. It is stated that a similar law seems to hold for root forma- 

 tion, and perhaps for other cases of regeneration observed but not discussed in 

 this note. 



The generality that the quantity of regeneration in an isolated portion of 

 an organism is, under like conditions and in equal time, proportional to the 

 mass of the growth-producing material circulating in the juices of the piece 

 and required for the synthetical processes giving rise to the regenerated 

 tissues and organs, is seen to be an expression also for rate of regeneration 

 and, in this form, a special case of the law for chemical mass action. 



The fact established by recent studies that such mass action, in case of a 

 given bud, is possible only after the portion of the stem supporting it has been 

 isolated is explained on the assumption that the growing apex and leaves of an 

 intact plant furnish some sort of substance which acts as inhibitor to the 

 buds below such apical or foliar portions as regards their utilization of such 

 growth material until isolation therefrom is effected. Thus the two main 

 factors operating in such cases are held to be chemical mass action and elabora- 

 tion of inhibiting substances by rapidly growing cells. 



Statistical studies of flower number per head in Cichorium intybus: Kinds 

 of variability, heredity, and effects of selection, A. B. Stout and Helene M. 

 Boas (Mem. Torrey Bot. Club, 17 (1918), pp. 334-458, pis. 4, figs. 5).— Employ- 

 ing largely the same material as in previous reports (B. S. It., 38, p. 226), the 

 author has studied the behavior of 0. intybus, finding that the number of 

 flowers hereditarily produced per head may range on a given plant from 7 to 31. 



Variations within the individual are continuous rather than discontinuous. 

 Position seems to be a factor influencing flower number. The number of 

 flowers per head shows much individual variability. The total number of 

 flower heads and length of blooming period appear to be correlated with vegeta- 

 tive vigor, variations of this sort being noted even in closely inbred and very 

 uniform races. Much more fundamental differences exist between plants of 

 different races or between races as such. The individual variations observed 

 are to be considered as fluctuating and continuous and to indicate that the 

 character of flower number is constantly varying, giving differences upon 

 which selection may operate in the isolation of races. 



Methods are indicated of attacking the problem as to the inheritance of 

 variations. The differences between varieties or races of chicory are as a 

 whole quite continuous. The operation of heredity in such a character as 

 flower number is seen in the isolation of races, which may be maintained by 

 such selection as was possible in chicory. Within each race, however, there are 

 further variations, continuous in gradation and of the same nature as those 

 appearing in a more mixed population. These are considered unmistakable 

 evidences of the instability of characters and hereditary units. 



Inheritance studies in Pisum. — III, The inheritance of height in peas, 

 O. E. White (Mem. Torrey Bot. Club, 17 (1918), pp. S16-S22, fig. I).— In this 

 portion of the present series (E. S. R., 38, pp. 226, 822), the author has given 

 attention to the fact that in certain cases the inheritance of height is more 

 complex than would be supposed from the results obtained by Mendel. Cases 

 of this sort are cited, as are some results of studies by the author continued 

 during several years on height, internode length, and internode number as indi- 



