682 



LIGHT AND LIFE 



transfer to fresh M medium, like those in the second line of Table 2. 

 The experiment was grown luider standard conditions and dissected 

 after 10 days, with the results shown in Fig. 3. The short-day stocks 

 showed no flowering in fresh Af medium, flowered in EDTA as ex- 

 pected, and flowered about equally in the "old" medium, thus appear- 

 ing to answer the first question. The long-day stocks were similar to 

 the short-day in their responses to M and EDTA media, but showed 

 higher FL% values in the "old" medium. This unexpected result 

 appears to confound the first and second question by suggesting that 



70- 



< 



3 5- 



Fig. 3 



FRESH 



rij- 



EDTA 

 3XI0'5 

 M 



n 



OLD 



SD STOCKS 



FRESH 



I ■ ^ ' I 



EDTA 



3XI0"5 



M 



OLD 



L D 



STOC K S 



Fig. 3. Flowering of L. nibba C.3 under continuous light in fresh M medium, 

 the same with 3 X ^^^' M EDTA, or "old" M medium. Cultines started either 

 from SD stocks grown on M mediinn with sucrose in 8-hour photoperiod or from 

 I.D stocks grown with frequent transfers to fresh M medium (no sucrose) in con- 

 tinuous light. Divisions of bars represent values deri\cd from one culture. Range 

 of frond numbers pev flask on day 10: Fresh, 117-14fi; FDTA, Orj-lO'); old, 63-77. 

 See Experimental, B4. Exp. 2-22-60. 



EDTA and "old" medium act differently on the two stocks, or, con- 

 versely, that the two stocks respond differently to the two media. 

 While such results require repetition and expansion, they appear 

 sufficiently reliable to present here. It should be noted, however, 

 that the pretreatments of the two stocks used differed in total light 

 quantity and presence or absence of sucrose as well as in photoperiod, 

 so that the difference need not be ascribed to the latter factor. Data 

 for the third point in question are not included in Fig. 3, since 

 growth in the previously inijilanted but aged mediinn was extremely 

 poor and iron-deficient in a])j)carance, probably because the iron 

 precipitated from solution dining the 12-day period (cf. 13). It was 



