78 



SCIENCE. 



[N. S. Vol. I. No. 3. 



(3.) A stem of Wistaria 1.75 meters 

 long and having seven internodes dropi^ed 

 mercury from seven vessels. Another stem 

 three meters long and containing forty- 

 seven internodes was first killed by heating 

 for an hour in water at 90°, and then dried. 

 This did not let mercury through until it 

 had been shortened to 2.5 meters. Then it 

 di'opped pretty fast from four vessels. Ee- 

 duced to two meters, nine vessels dropped 

 mercury, and out of some it ran rapidly. 

 Another shoot gave nearly the same re- 

 sults. A fresh and very long stem had to 

 be shortened to three meters before mercury 

 came through. Then it dropped from three 

 vessels. Successively shortened, the num- 

 ber of permeable vessels was as follows : 2.5 

 meters, eleven vessels ; two meters, eighteen 

 vessels ; 1.5 meter, twenty-seven to twenty- 

 nine vessels. These stems were one to two 

 centimeters thick. Conclusion : Some of the 

 vessels in Wistaria are quite long, though 

 scarcely more than three meters. Most of 

 the wide vessels are about one meter long. 



(4.) A cane of Vitis Labrusea 1.2 centi- 

 meter thick, which was previously killed 

 by heating for an hour in water at 90° C. 

 and then air-dried, first let mercury through 

 (3 vessels) when shortened to 2.2 meters. 



(5.) A shoot of Aristolochia Sipho 1.5 cen- 

 timeters thick, 2.5 meters long, and having 

 fifteen internodes was kUled in the same 

 way. This let mercury through foui'teen 

 vessels. Another shoot 2.1 meters long let 

 the mercury through many vessels. A fresh 

 stem five meters long, the longest he could 

 get, dropped mercury from five vessels. 

 "When successively shortened, more and 

 more vessels dropped mercuiy. At 3.5 me- 

 ters twenty-five vessels let it through, and 

 when the stem was cut down to three me- 

 ters the number of vessels dropping mercury 

 coidd not be determined. Conclusion: In 

 this plant numerous vessels are three meters 

 long, some are five meters long, and a few 

 are probablj'^ longer. 



In Aristolochia the vessels of different an- 

 nual rings were equallj^ j)ermeable, but in 

 the wistaria, the locust and the oaks the 

 permeable vessels were mostly on the per- 

 iphery. The records were made in from ten 

 to thirty minutes fi-om the beginning of the 

 pressure, the tune depending on the length 

 of the stem. In general the mercuiy was 

 passed through the stem in the same direc- 

 tion as the ascending water current, but a 

 change of direction did not give contradic- 

 tory results. These experiments were re- 

 jjeated, usmg a pressure of forty centime- 

 ters, but even this did not rupture anj' cross- 

 walls. This increased pressure overcame 

 the capillarjr resistance and forced the mer- 

 cury through many smaller vessels, but 

 otherwise the results were much the same. 

 Erwin F. Smith. 



Washington. 



SCIENTIFIC LITERATURE. 

 Introduction to Elementary Practical Biology. — 

 By Charles Wright Dodge, M. S.— Har- 

 per Bros., New York. 1894. 

 This book is a laboratory guide for high 

 school and college students. The teacher 

 of biology who is endeavoring to train his 

 students in the best manner is in modern 

 times, amid the abundance of laboratory 

 guides, in veiy much of a quandary as to 

 the best of two opposite methods. If, on 

 the one hand, he puts a laboratory guide 

 into the hands of the student, the result is 

 apt to be that the student soon learns simply 

 to verify the facts mentioned in the book, 

 and thus loses all stimulus for original ob- 

 servation, which should be the foremost 

 result of practical work in biological science. 

 On the other hand, if the teacher gives to an 

 elementary student a specimen to study 

 without laboratory dii-ections, he is at such 

 complete loss to know how to proceed, what 

 to do, and particularly what points to no- 

 tice, that a large proportion of his time is 

 wasted through sheer lack of the proper 



