126 TJniversity of California Publications in Botany [Vol. 5 



III. TECHNIQUE AND METHODS 



1. Obtaining "Pure" Seed 



In obtaining "pure" seed — naturally self- (close) pollinated 

 or artificially self- (close) pollinated seed from the protected 

 flowers of a parent or a plant of the F^ (or subsequent hybrid 

 generations) — a vigorous lateral near the top of the main axis 

 of the plant is selected and prepared by stripping off leaves, buds 

 and small branches for a distance of a foot or more below the 

 terminal buds and flowers. The choice of a lateral on the 

 upper two-thirds of the main stem means nearly total absence 

 of the seed which in the case of lower branches falls from above 

 and adheres to the sticky, minutely glandular epidermis. AH 

 opened flowers and all but three or four buds are then picked 

 off the terminal inflorescence with forceps and a fresh paraffin 

 bag, placed over these remaining buds and secured at the base 

 with a copper-wired pot label suitably marked, allows sufficient 

 room for a number of flowers to expand normally and effectually 

 excludes the entrance of foreign pollen b}' practically any agency. 

 As mentioned above, self fertilization is accomplished readily and 

 in the majority of cases, after the bag has been carefully opened 

 at the end of two or three weeks to make sure that seed is being 

 set, no further attention need be given the material until the 

 seed is gathered at the end of another two or three weeks. In 

 this connection it might be said that, in the case of .V. acuminata 

 the ripe seed often begins to fall from the promptly 2-cleft apex 

 of the capsule while the lower two-thirds of the maturing ovary 

 is still green. The semi-transparent paraffin bag makes it pos- 

 sible to watch the development of the capsule without opening 

 the bag. If the seed capsule is gathered and hung to dry when 

 the tip of the capsule first begins to show a brownish coloration, 

 the seed ripens perfectly within the capsule and danger of a 

 mouldy condition of the seed is eliminated. 



In gathering seed the lateral is cut three inches below the 

 bottom of the bag. placed and wired in a larger heavy manila 

 bag with the pot label showing, and hung to dry out of doors. 



