416 



SCIENCE. 



[N. S. Vol. XIX. No. 480. 



are satisfactorily stained, the mixture is 

 transferred to a filter and the excess of 

 stain is removed as quickly as possible by 

 washing the magma with water; the ma- 

 terial is then allowed to dry spontaneously, 

 and mounted in Canada balsam, both the 

 preparations and the dried material being 

 permanent. 



The foregoing method has features simi- 

 lar to the method used for demonstrating 

 the so-called continuity of protoplasm in 

 the vegetable cell-wall, and those who are 

 interested in the latter subject will do well 

 to compare their preparations with those of 

 the wheat starch grain, made by the method 

 just described. 



On an TJnde scribed Thermometric Move- 

 ment in the Branches of Woody Plants: 

 Professor W. F. Ganong, Smith College. 

 Some years ago the author observed a 

 definite radial or in-and-out movement of 

 the ascending branches of certain shrubs 

 in winter, and undertook a systematic study 

 of the movement, which appears not to have 

 been investigated hitherto. By means of 

 accurate measurements made with steel 

 tapes from a central permanent tripod, the 

 exact amount of the movement was deter- 

 mined for several shrubs and small trees. 

 The results, when plotted, not only showed 

 the movement to be real and of considerable 

 amount, but also proved that the inward 

 movement increases steadily after leaf fall 

 till past midwinter, when an outward move- 

 ment commences, long before the weight 

 of the leaves begins to be felt. Further- 

 more, the important fact was discovered 

 that the movement shows remarkable in- 

 and-out secondary fluctuations, which are 

 closely correlated with temperature changes. 

 Experiments undertaken to determine the 

 physical basis of the movement eliminated 

 one possible cause after another until it 

 was determined that it Avas correlated with 

 the percentage of water in the stems, this 



rising with a higher and falling with a 

 lower temperature. It was proved that the 

 weight of this water was insufficient to 

 cause the entire movement though it does 

 influence it, and evidence was given to show 

 that the movement is probably due to the 

 swelling of the parenchyma cells of cortex 

 and pith under the osmotic absorption of 

 the water permitted by the increased sup- 

 ply conducted up the stems in the periods 

 of warmer weather. This swelling of the 

 cells causes a straightening of the branch 

 and hence the outward movement. The 

 movement appears, therefore, to have no 

 ecological significance but to be simply the 

 incidental result of the physical and me- 

 chanical construction of the stems, but it is 

 a new and interesting phenomenon. As it 

 is an incidental result of, and closely de- 

 pendent upon, temperature changes, the 

 author has named the movement thermo- 

 metric. 



The Olive Tubercle (illustrated by stereop- 

 tieon photographs and inoculated speci- 

 mens) : Dr. Erwin F. Smith and Mb. 

 James B. Rorer, Department of Agri- 

 culture. 



This disease was taken up because its 

 bacterial origin has recently been called 

 in question by Dr. Fischer. After describ- 

 ing the disease, which has been known for 

 many centuries in Europe and has recently 

 done much damage in California olive orch- 

 ards, the experiments of Savastano and 

 others were outlined, and then those under- 

 taken in Washington. Tubercles were ob- 

 tained from California. No difficulty was 

 experienced in plating out bacteria or in 

 finding them in the tissues on microscop- 

 ical examination. They occurred abund- 

 antly in small irregular pockets. No fungi 

 were present. From small knots pure cul- 

 tures of a white bacterium were plated out, 

 and with this organism the knots were re- 

 produced. The olive trees used were small 



