Parthenogenesis and Vegetative Apogamy 119 



and even when only one appears, as is usually the case, 

 how can it be certain that it has arisen from an act 

 of fertilization? One can assume for the most part 

 that embryos are the result of fertilization, but the 

 increasing number of cases of apogamy introduces a 

 serious element of uncertainty. If two individuals 

 have been crossed, and the expected results in the F, 

 or F2 generations do not appear, how can it be told 

 whether the pollen parent has entered into the result 

 at all? Doubtless puzzling results in genetics have 

 arisen more than once through apogamy; the crossing 

 has been controlled, but the results are taking place out 

 of sight and of course out of control. The crossing is 

 only the gross part of the performance. If instead of 

 applying pollen to stigma one could apply sperm to egg, 

 there would be far more control. The program of events 

 between pollination and fertilization should be kept in 

 mind, and also the program between fertilization and 

 the escape of the embryo from the seed. Not a single 

 stage of these performances is under observation, much 

 less under control. Pollination is effected, and then the 

 plant emerging from the seed is observed. One must 

 take for granted that all of the numerous events that 

 lie between have been completely orthodox. Usually 

 they are, but sometimes they are not; and then the 

 unexpected result is forced into the orthodox program. 

 It is really surprising, with so much of our experi- 

 mental work out of sight and beyond control, that so 

 many constant results are obtained. It is an impres- 

 sive lesson as to the wonderful uniformity of conditions 

 between polUnation and fertiUzation, and then between 

 fertilization and embryo escape. This gives assurance 



