1922] KNUDSON—ORCHID SEEDS 5 
from four to six months. Under greenhouse conditions this 
advanced stage has apparently been attained in some cases in a 
shorter time. 
Methods 
Unless otherwise indicated, all cultures were made using agar 
slopes in culture tubes 180mm.X18mm. The nutrient solution 
used was either Pfeffer’s or a modification referred to hereafter 
as solution B. The solutions were made up as follows: 
SOLUTION B PFEFFER’S 
Ca(NO;)2, 1 gm. Ca(NOQ,)., 4 gm. 
K,HPOQ,, 0.25 gm. K.HPO,, 1 gm. 
MgSO,7H.0, 0.25 gm. MgSO,7H.0, 1 gm. 
Fe,(PO,);, 0.05 gm. KNO,, 1 gm. 
(NH,).SO,, 0.50 gm. KCl, 0.5 gm. 
Distilled HO, 1 1. FeCl,, 40 mgm. 
Distilled H,0, 5 1. 
Solution B was used because BurRGEFF stated that the orchid 
seeds utilized ammonium sulphate to better advantage than the 
nitrate salt. My own experience is not in accordance with this. 
Generally 1.50 per cent agar was used, and all media and vessels 
were autoclaved at fifteen pounds pressure for thirty minutes. 
To prevent the lodging of spores and microorganisms on the 
cotton stopper of the culture tube, it was capped with a small 
vial which, fitting tightly over the cotton plug, inclosed the upper 
third of the tube. The use of the vial cap was essential because 
otherwise, under the moist greenhouse conditions, contamination 
resulted from spores growing down through the cotton plug or 
between the plug andsthe tube. By using the vial cap cultures 
remained pure even after a year in the greenhouse. 
The cultures were all grown under aseptic conditions. For 
sterilizing the seeds, the calcium hypochlorite method of Witson 
(13) was used. For this purpose 10 gm. of calcium hypochlorite 
was added to rgocc. of distilled water. This was vigorously 
shaken for a few minutes and then filtered. The clear filtrate was 
used for sterilizing the seeds. The quantity of seeds desired was 
placed in a small test tube and the clear filtrate added. The tube 
was then shaken until each seed became moistened with the solution. 
