OTHER ISOLATION TECHNIQUES 19 



he brought a needlepoint, held in the hand, near a spore. The 

 spore could be seen to attach itself to the needle and could then 

 be planted on agar to permit germination and subsequent growth. 



Other isolation techniques. In isolating aquatic fungi, 

 notably Saprolegniales, a small quantity of swarm spores or en- 

 cysted spores may be suspended in water and put into an atom- 

 izer. Some of these spores may then be forced througrh the 

 atomizer, so that they are deposited in tiny droplets on the 

 surface of agar plates. Here they germinate, and marked spore- 

 lings can be transferred to slanted tubes of agar. 



The isolation of Chytridiales may require a more elaborate 

 technique. Couch (1939) recently isolated certain chytrids, 

 including Rhizidiomyces apophysaWs, Rhizophidiiun carpo- 

 phihmi, and R. imiltipormu. He placed the materials containing 

 these chytrids, namely, decayingr leaves and s^rass, in distilled 

 water to \\hich activated charcoal had been added. Into this 

 were placed, as bait, boiled bits of corn leaves or grass blades. 

 After 2 or 3 days the bait was examined, and, if chytrids occurred 

 within the tissues, the fragment of leaf Mas \\ashed in a stronsf 

 Stream of w^ater. A fragment containing chytrids w^as then ex- 

 cised and placed in a drop of water in a Petri dish. With the 

 aid of a binocular single sporangia were dissected out and placed 

 in a fresh drop of water baited with a fresh bit of leaf frag- 

 ment, and again a single sporangium could be dissected out and 

 dragged over agar to free it from bacteria, or zoospores could 

 be picked up by means of capillary pipettes. Eventually pure 

 cultures could be isolated by these procedures. Berdan (1941) 

 employed this procedure in isolating Cladochytrhnn hyalimim in 

 pure culture on agar. 



The ascospores are explosively discharged by many species of 

 Pyrenomycetes and Discomycetes. Advantage may be taken of 

 this fact in isolating them in pure culture. The tissues, bearins^ 

 perithecia or apothecia, should be placed in the tops of inverted 

 poured plates of agar. Bits of wet paper toweling or other 

 absorbent paper placed beneath the plant tissues will serve to 

 keep the tissues moist, provide a high relative humidit\% and 

 brincT the fruit bodies sufficiently near the surface of the aijar 

 above to be within range of the ascospores when dischars^ed. If 

 proper conditions are provided, the ascospores on expulsion, 

 singly or en masse, adhere to the agar, and are free from con- 



