April 12, 1918] 



SCIENCE 



365 



drawing on the blackboard. In the first case 

 the good teacher usually feels there is a failure 

 of full elucidation on his part, while in the 

 second case valuable time is lost, and a break 

 is made in the lecture. 



To overcome this difficulty the writer re- 

 cently devised a simple plan to make line 

 drawings and diagrams on glass slides to be 

 used as regular lantern sides. Clean lantern 

 slide covers are taken, and on them the ob- 

 jects desired are drawn with a " china mark- 

 ing pencil." One must not lift the i)encil 

 from the glass while drawing, or else use 

 great care at the points where the pencil is 

 lifted and the same line then continued. It 

 is not necessary to make an absolutely black 

 line, as any mark shows plainly. A few trials 

 will show how sharp one's jyeneil should be 

 for the best results. As wide a margin must 

 be left as in making ordinary slides. If a 

 mistake is made it can be erased with the 

 finger or a blunt piece of wood. The mark 

 does not rub out too easily, consequently the 

 slides can be used without the further trouble 

 of covering if they are to be of a temporary 

 nature. However, they can be fi^ed perma- 

 nently by finishing them in the usual way 

 with a clean cover slip and bound with tape. 



As the "' china marking pencils " come in 

 at least three colors, black, blue and red, and 

 as their cost is slight (15 cents) and the whole 

 process is simple and short, their use in this 

 way is practicable and inexpensive. The 

 pencils can be purchased at any good station- 

 ery store. 



Horace Gunthorp 



Department of Botany, 

 University of Minnesota 



a suggestion for making thin sections 

 for bryozoan slides 



In making thin sections for bryozoan slides 

 it has been noted by the writer that many of 

 them have a frosty, crystalline appearance 

 when they have been ground to the desired 

 thickness. In the process of grinding, numer- 

 ous small particles of calcium carbonate are 

 forced into the openings, obscuring the struc- 

 ture. As these fine particles have relatively 

 large surface exposure, they will dissolve much 



more readily than the rest of the fossil when 

 treated with dilute hydrochloric acid. It is 

 best to let the acid act for only a very short 

 time and then wash it off quickly, repeating 

 the treatment several times, if necessary, until 

 the structure stands out clearly. 



Charles E. Decker 

 University of Oklahoma 



a national floral emblem 



Xow that America is engaged in the grim 

 business of war for the defense of democracy, 

 we are tempted in our zeal to forget the things 

 which are purely sentimental because of the 

 pressing needs of the things practical. 



But with the dreaded arrival of casualty 

 list?, the great heart of the nation has been 

 deeply stirred, the grief of America stands in 

 yearning need of sentiment. And so senti- 

 ment — pure sentiment — sponsors the thought 

 that the American people have a real need for 

 a recognized national floral emblem. 



When the cherished day of peace arrives, 

 how shall we greet our boys returning from 

 the front ? With flowers ? Of course, but how 

 with flowers? Goldenrods? Daisies? Vio- 

 lets? Yes, with all of these, but national 

 sentiments might well be crystallized on a 

 single national symbolic flower. 



The rose of old England, the Fleur-de-lis 

 of France, the thistle of Scotland, the chrys- 

 anthemum of Japan; all these remind us that 

 America at present does not possess a floral 

 emblem to epitomize the things that are noble 

 and good in the nation. 



Why should not all that is best in the Amer- 

 ican nation be symbolized in a flower as a na- 

 tional emblem? The very mention of such a 

 symbol should stir the depths of patriotism 

 in the breast of every true American. Surely 

 Germany is the loser by not having a well- 

 known floral emblem. In Europe, America has 

 been criticized for being too material — would 

 not the adoption of a national flower be an 

 esthetic step in the right direction? 



If, then, it is agreed that America will 

 be benefited by possessing a recog^nized na- 

 tional floral emblem, the selection of a suit- 

 able flower is a difficult task indeed. The 

 flora of the country is so rich that the choice 



