September 29, 1922] 



SCIENCE 



367 



grown in artificial light entirely. Since no 

 reference to the growth of plants from seed to 

 seed without sunlight has been found in the 

 literature this preliminary report of the first 

 successful attempt may be of use to plant 

 breeders and agronomists in northern regions. 



A great variety of plants including several 

 varieties of wheat, oats, barley, rye and pota- 

 toes, buckwheat, lettuce, beans, peas, clovers, 

 radishes, flax and a number of common weeds 

 were grown from seed to seed entirely in arti- 

 ficial light. The seed produced was of good 

 quality, full of starch, and germinated well. 



Light for the experiment was obtained from 

 tungsten filament nitrogen filled lamps which 

 were burned for twenty-four hours each day. 

 The lamps are rated to burn 1,000 hours but 

 they averaged 3,000-4,000 hours under continu- 

 ous use. One set of lamps was found to be 

 more than sufficient to produce an ordinary 

 crop such -as the cereals, since the time to head 

 is much decreased by continuous illumination. 

 Spring wheats produced ripe seed in about 90 

 days. At this rate it ought to be possible now 

 to grow three generations from a cross within 

 one year. The growth of valuable plants in 

 artificial light should be of considerable advan- 

 tage in northern regions where the light in 

 winter is of short duration and low intensity. 



All of the plants tested, except cabbage, have 

 bloomed and each variety does not seem to re- 

 quire any particular period of illumination to 

 cause blooming as found iby Garner and 

 Allard.i 



Four ranges of light intensity were used 

 and a number of plants bloomed in all of them, 

 although the illumination was continuous. The 

 tests were performed in three unheated base- 

 ment rooms. It was unnecessary to supply any 

 heat other than that produced by the lamps 

 even in the coldest winter weather. For cereals 

 the temperature was controlled automatically 

 at 14° C. by blowing in cold outside air. The 

 energy used in heating the ordinary green- 

 house in Minnesota during the winter would 

 be ample for both light and heat in such experi- 

 ments as these since nearly all the energy of 



1 Garner, W. "W., and Allard, H. A. : Jr. Agr. 

 Bes., 18: 553-606: 1920. 



the light finally goes to heat and thus is made 

 to serve a double purpose. 



E. B. Harvey 

 IJNiVERsrrY or Minnesota 



THE PREPARATION OF CLEAR BEEF AGAR 

 A CLEAE beef agar with a pg reading from 

 6.6 to 7.0 being desired and the usual method 

 for the preparation of such media proving un- 

 satisfactory, inasmuch as a cloudiness often 

 developed in the cleared agar on sterilization, 

 the following procedure has been adopted and 

 has proved uniformly reliable. 

 The formula is as follows: 



Beef extract (Liebig's) 3 grams 



Peptone ("Bacto") 10 gi-ams 



Sodium cUoride 5 orams 



Agar Agar 15 gj-^ms 



These ingredients are dissolved in one liter 

 of distilled water by flowing steam. As sug- 

 gested by the directions for the preparation of 

 beef bouillon, given by James Mcintosh, M.D., 

 and William A. M. Smart, B.Sc.Land.,i the 

 resultant nutrient agar is adjusted to a pn of 

 about 8.2 with an approximately normal solu- 

 tion of sodium hydroxide. After cooling to 

 45°-50° C, the beaten whites of two fresh eggs 

 are added. Soluble egg albumin powder may 

 be substituted for the fresh eggs, 5 grams 

 beaten up in 50 cc. of distilled water proving 

 satisfactory. If more than one liter is being 

 made, the beaten white of one egg or a. pro- 

 portional quantity of egg albumin powder 

 should be used for each additional liter. After 

 mixing thoroughly by pouring from one con- 

 tainer into another, the agar and egg are auto- 

 claved for 15 minutes at 15 pounds pressure, 

 filtered through paper or, preferably, through 

 absorbent cotton by suction, and the filtrate 

 adjusted to the desired pjj with an' approxi- 

 mately normal solution of hydrochloric acid. 

 It is then autoclaved for 5 minutes at 15 

 pounds pressure to insure the complete pre- 

 cipitation of any fine particles remaining in 

 suspension and filtered through paper. After 

 tubing, it is finally sterilized for 20 minutes at 

 15 pounds pi-essure. This beef agar remains 



1 James Mcintosh and William A. M. Smart : 

 "The Adjustment of the Reaction of Bacteri- 

 ological Media," Lancet, Vol. CXCVII, No. 5017. 



