128 University of California Puhlications in Botany [Vol. 5 



In the profusely branching species of Nicotiana much care 

 is necessary in picking all buds out of the axils of leaves and 

 thoroughly stripping the lateral chosen on the female parent so 

 that small branches and flowers may not develop within the bag 

 while the hybrid seed is being formed. The lateral is carefully 

 gone over with the scissors and usually only one bud on the 

 terminal inflorescences is left. The hands and instruments are 

 now sterilized again. With the forceps the corolla tube is 

 carefully split from the top of the calyx teeth to the corolla 

 lobes, or until the corolla can be gently pushed liack and the 

 stamens and pistil exposed. The unopened stamens, one or two 

 at a time, are then pinched off with the forceps half way down 

 the filament, or often the anthers themselves are picked out 

 separately. The corolla can now be closed back and around 

 the pistil, the effort being to mutilate and derange the normal 

 condition and position of the perianth as little as possible. A 

 bag covers the castrated bud and the label attached to the bag 



]_50 

 carries the plant number and the female sign — e.g., 07 $• It 



may be mentioned here that this label remains with the bag 

 while on the plant, during the drying of the seed, and is placed 

 in the seed envelope when the seed is cleaned. A number of 

 such castrated buds are prepared and often the date and hour 

 is noted on the labels attached. References to all such opera- 

 tions are, of course, placed in the record book for the particular 

 experiment. 



These flowers in both the parents will be ready for use in 

 two or three days. When the two parents have been prepared 

 at about the same time and the buds are of the same size I 

 usually watch the pollen parent, since, as noted above, the 

 stigma is practically sure to be receptive as soon as the anthers 

 are open. This holds true for each of the three varieties of N. 

 acuminata as well as for different flowers on the same plant. 

 The developing buds can be seen through the paraffin bag and 

 on the second day after bagging, when the corolla of the pollen 

 parent is fully extended, it may be safely assumed that condi- 

 tions are favorable in both parents for cross-pollination. 



The lateral upon which the male parent has been bagged is 



