152 CARL DOWNEY LA RUE 



selected it was found that the spores produced by the mycelia from these 

 spores were entirely normal in regard to cell number. 



The range of variation in number of spore appendages is even less than 

 that in cells. The greatest number recorded from all observations made 

 was four and the smallest number, one. Three different spores were iso- 

 lated which bore only one appendage each. However, when these spores 

 germinated and the mycelia from them produced spores, the latter were 

 found to have the normal three appendages. Another spore bearing two 

 appendages was isolated with the same result, and still another bearing 

 four appendages gave progeny which showed no sign of this abnormality. 

 Apparently variation in cell number and spore appendage number are not 

 greatly different in behavior from sundry other abnormalities which appear 

 from time to time in Pestalozzia, none of which appears to be hereditary. 



Selection of spores according to their progeny 



The method of procedure in selecting spores according to their progeny 

 was as follows : A single spore culture was made from a given strain. When 

 this culture produced mature spores agar plates were poured with various 

 dilution^ of these spores. A mass of spores was taken from the culture 

 with a platinum wire and mixed with about 10 ~cc of sterile water in a 

 sterile tube. From this water suspension of spores two loops were put into 

 a tube of melted agar and thoroughly mixed. Two loops of this agar were 

 then mixed in the next tube; and again two loops were used to inoculate 

 the third tube. The agar from each tube was then poured into a sterile 

 petri dish, and the dish was covered with a bell jar. When the spores 

 germinated the agar plates were examined and spores were cut out from 

 the most suitable ones and put into separate tubes of Hevea agar. Micro- 

 scopic examination was made in each case to make sure that only one 

 spore was used in inoculating each tube. On this account it was found 

 more convenient to use a 1 -percent beef-extract agar instead of Hevea 

 agar for pouring the plates. It was not always possible throughout the 

 experiments to regulate the number of spores in the poured plates. The 

 third dilution plate was the one from which the spores were usually taken, 

 but whenever this contained too few spores to make a full set of cultures 

 for a given generation, the second dilution plate was used instead. 



All the tubes contained agar made in one lot, tubed and sterilized at the 

 same time, and stored under the same conditions. The transfers of the 

 twenty single spores were made one immediately after the other, so that 

 the time of transfer of each was so nearly the same as to admit of no 

 reasonable assumption that this variation could be of effect. The twenty 



