LABORATORY AND TEACHING METHODS 647 



and are ready for inoculation, experiments may be tried on all three of these plants. 

 Inoculation with this fungus should be made into the roots of these plants, just below 

 the soil of the experimental pots. The soil should be removed and the tops of the 

 roots laid bare. Inoculation can be made by incisions into the root into which the 

 mycelium or spores of the fungus are rubbed. After inoculation the soil can be 

 returned to its place. 



LESSON 33 



Knot of Citrus Trees (SphiBropsis iumefaciens) . — Successful inoculations have been 

 made on lime, pomelo, lemon, tangerine and hardy orange {Citrus trifoliata) . 



First Method. — Make a small T-shaped cut in the back of a lemon or orange tree 

 with a sterile knife and insert some mycelium. Smooth the bark down and bind 

 the stem with raffia to cover the wound completely. 



Second Method. — Inoculate by pricking the stem three times with a sterile cam- 

 bric needle fixed in a wooden handle, then place a little mycelium over these punctures 

 and bind with raffia. 



Third Method. — Inoculate by cutting oflf a very small amount (2 or 3 sq. mm.) of 

 the outer bark, then spread the mycelium over this injury and bind it with raffia. 

 A year may elapse before the galls are fully formed. 



Consult Hedges, Florence, and Tenny, S. S.: A Knot of Citrus Trees Caused 

 by Sphaeropsis tumefaciens. Bull. 247, Bureau of Plant Industry, 191 2. 



Clover Disease. — Select either red, white, or alsike clover plants somewhere in 

 a protected place in the garden, or as potted plants in the greenhouse, and inoculate 

 with Bacillus lalhyri. The inoculation may be made by an atomizer. Make a 

 suspension of the organism in distilled water by means of several loopfuls stirred in 

 the water. Spray the clover plants with the water and cover with a bell jar for a 

 few days (J. J. Taubenhaus). 



LESSON 34 



Sweet Pea Diseases (J. J. Taubenhaus). — Take several potted sweet pea plants 

 and spray the leaves by means of an atomizer, which has been sterilized previously 

 by boiling in water. Make a suspension of the spores of Glomerella rufomacuians 

 in water and spray this water upon the sweet pea plants which should then be 

 covered with a bell jar. Study the stages of spore germination and spore inoculation 

 by sacrificing daily one of the sprayed plants. 



Inoculate the seeds of sweet pea varieties with cultures of Fusarium sp. and 

 Corticium vagum by immersing the seeds in water containing a suspension of fungous 

 spores. To get this suspension stir up the separate cultures in a sterile watch glass 

 in distilled water. Then dip the seeds in this water and plant the seeds in loamy 

 soil in pots for greenhouse culture. Follow the germinaUon of the peas and the 

 progress of the disease, thus communicated to the plants. 



Inoculate the sweet pea by placing a pure culture of root-rot, Thielavia basicola 

 on the roots of sweet pea plants. Another method adapted to prove the patho- 

 genicity of the fungus is to sow pure cultures of it on sterilized seeds (seeds treated 

 with s per cent, formalin for one-half hour) in sterile pots and soils. 



Inoculate seedlings of sweet pea with Chxlomium crispatum by soaking the seeds 



