486 



SCIENCE. 



[N. S. Vol. III. No. 65. 



the perusal of any scientist, no matter in what 

 direction his interests may be enlisted. 



Following this are chapters on the differenti- 

 ation of simple functions; integral calculus and 

 its applications; higher differential equations 

 and the functions of variables; infinite series 

 and Taylor's series; the theory of maxima and 

 minima ; solution of numerical equations ; ex- 

 amples from mechanics and thermo-dynamics. 

 Collections of problems and formulae precede 

 the index, which completes the volume. 



The aim of this book is fully expressed by its 

 title ; its scope is indicated by^the above sum- 

 mary of its contents. 



Although not a pioneer in this particular 

 field — A. Fuhrmann's Naturwissenschaftliche 

 Anwendungen der Differential-rechnung was 

 published in 1888, the appearance of this 

 treatise must be pronounced most opportune. 

 It is certainly deserving of a cordial welcome, 

 and mastery of its contents can not fail to be of 

 great value to all who have not already appre- 

 ciated the important bearing, of the higher 

 mathematics on numerous problems of natural 

 science. Ferdinand G. Wiechmann. 



SOCIETIES AND ACADEMIES. 

 BIOLOGICAL SOCIETY OF WASHINGTON — 257TH 

 MEETING, SATURDAY, MARCH 7. 

 A PAPER on the Influence of Fruit-bearing 

 upon the Mechanical Tissue of the Twigs, by 

 Adrian J. Pieters, was, in the absence of the 

 author, read by George H. Hicks. The au- 

 thor's conclusions, based on a study of twigs of 

 the apple, pear, peach and plum were that 

 the one-year-old fruit-bearing shoot of the 

 apple and the pear has less wood in proportion 

 to its diameter than does the vegetative shoot 

 of the same age. This is due, in the apple 

 largely, and in the pear solely, to a great in- 

 creiase in the cortex of the fruit-bearing shoot. 

 It does not, however, appear from the struc- 

 ture of the shoots that the fruit-bearing shoot is 

 weaker than the vegetative. The former is 

 well supplied with supplementary mechanical 

 tissue which is distributed at those points 

 where it is most needed. This gives an in- 

 crease of strength for the fruit-bearing year, 

 which fully makes up for the small difference 



in xylem. In the peach the fruit-bearing shoot 

 has more wood than the vegetative, and the 

 walls of the wood cells are as thick in the 

 former as in the latter. 



In general it may be said that the effect of 

 fruit-bearing upon the tissues is local. In the 

 apple and pear it is felt throughout the one- 

 year-old shoot ; in the plum and peach it is con- 

 fined to a small area in the immediate neigh- 

 borhood of the fruit stalk. 



The local effect on fruit-bearing is towards 

 an increase of cells and a decrease in the 

 thickness and lignification of the walls of the 

 wood cells. The cortex is especially enlarged, 

 giving rise in the apple and pear to the char- 

 acteristic swollen condition of the fruit-bearing 

 shoot. 



In all cases the increase in growth is great- 

 est on the side near the fruit stalk, although 

 the wood in the apple and pear is best devel- 

 oped on the side of the lateral vegetative bud. 

 The effect which fruit-bearing exerts upon 

 the xylem disappears with time. The study of 

 apple shoots that had borne fruit in their first 

 year showed that in the two or four years fol- 

 lowing there had been a rapid increase of wood, 

 especially on the side of the fruit scar which 

 was weakest at the end of the first year. At 

 the end of three and five years these shoots had 

 a better xylem development than shoots of the 

 same age that had never borne fruit. 



Fruit-bearing has a local effect upon the lig- 

 nification of the walls of wood cells. It pre- 

 vents their lignification wholly or in part ac- 

 cording to their distance from the fruit stalk. 



The lignification of other cell walls is pro- 

 moted by fruit-bearing. In the fruit stalk the 

 greatest part of the tissue has become lignified, 

 and in the upper part of the apple and pear 

 shoots there is an abundance of sclerenchyma 

 and hard bast, which is either not found in the 

 vegetative shoots or only in small amounts. 



Dr. E. L. Greene presented a paper on The 

 Distribution of Shamnus and Ceanothus in Amer- 

 ica. Of the first named genus, the European 

 Bhamnus cathartica being its type-species, some 

 100 species are recognized, these being distrib- 

 uted all around the northern hemisphere, chiefly 

 within the temperate zone. In contrast with 

 Europe, which has 23, North America north of 



