188 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 13, No. 9 
50 per cent sphagnum moss, the medium being covered over with fine woven 
clean burlap and the flower pot when prepared being thoroughly sterilized in 
an autoclave. The third day after sterilization, if no infection manifested 
itself, the rhizoctonia was introduced to each of the experimental pots. 
Check pots were also kept for comparison. Moisture conditions were main- 
tained by placing saucers of water in the propagating frame. A temperature of 
80° to 85°F. with a relative humidity test of 75 to 82 per cent was maintained. 
The speaker had a few seedlings appear promiscuously on a few of the check 
pots which had not been infected. This may have been due to contamination 
as the check pots were placed side by side with those infected with the fungus. 
While several nutrient solutions were used, including Pfeffer’s, Burgeff’s, 
and Crones’, the culture giving the most satisfactory results was the one 
recommended by Burgeff, which is here given. 
Burgeff’s solution 
grams 
Potassium dihydrogen phosphate.; )).2. 8320 O22 Pak See 1.0 
Calenmm Chlorides. of.) 2) Be ee a eee 0.1 
MO iam! (CHLOT TMG iso ss ecsic nck eee ee I ee ct ces Re UE Pa 0.1 
Rraprcsiimn: BiLRbe? ee kbc. PRR a 05 ae Re ees See 0.3 
Tron Chloride: shea. e+ aces « < s 0. ek Re eae a ee ee 0.01 
ATHIMONIUIN COLOTICE: J. ok.) . Le ae ne ce ene ee ee een 0.5 
DIStULed Waletrerecewas te osc. ig ee CRM MRTIN Data c Lice Lye l: 27 nee: See eae 1000.0 
Other nutrient solutions such as sugars, from 1 to 2 per cent solutions, glucose 
gelatin and non-liquefiable nutrient (potato) were also used in the experiment. 
Roots growing in the air and roots from potted plants were utilized in 
making inoculations. The roots before using for inoculation and the seeds 
before being sown were subjected to sterilization by immersion for 2 to 3 
minutes in a 7 per cent solution of calcium hypochloride. 
Small pieces of the orchid root about $ inch long were used and fone 
to the Petri dishes and test tubes containing the nutrient agar. In the cases 
of the flower pots, the small sections of the roots containing the rhizoctonia 
were placed under the burlap. 
Out of a series of several hundred cultures only two organisms occurred 
with any noticeable regularity. Average contamination was manifest both 
in the test tubes and also in the flower pot method. 
It is the opinion of the speaker that orchidaceous plants having a long line 
of ancestors and being the most specialized of all plants are necessarily de- 
pendent on other than ordinary food and environmental conditions which 
govern the life cycle of the masses of the lower plants. The orchid seed is 
very minute and devoid of endosperm. It has therefore acquired the habit of 
depending on the various root fungi for its early existence. 
Further investigation with a large number of generic crosses demonstrated 
that a separate organism is required for a particular genus and possibly for 
particular species. As some results were obtainable under aseptic conditions 
‘it can not be said that the fungus is entirely essential but it is incontestable 
that the rhizoctonia promotes the germination of the seeds. It is nevertheless 
true that its presence is not indispensable and that a satisfactory germi- 
nation can be obtained without its introduction. 
Symbiosis opens up a wide field for investigational work and progress 
along this line is reaching more definite conclusions and perhaps we may 
find that a ‘well balanced ration” or the proper proportioning of plant food 
in each case for genera and species will reveal the “undiscovered secret of 
