EXPERIMENTAL EMBRYOLOGY 397 



bryony has been known in this genus for a long time, but fertiliza- 

 tion is essential for the production of the embryos. Unpollinated 

 flowers wither and fall away without forming seeds (Strasburger, 

 1878). 



Fagerlind performed three sets of experiments. In the first he 

 pollinated some of the pistils with a large quantity of pollen and 

 others with a small quantity of it; in the second he used foreign 

 pollen; and in the third the ovaries were treated only with growth 

 hormones. Those pistils which had received an adequate quantity 

 of pollen set seeds normally, the embryos being of nucellar origin. 

 In others, where the amount of pollen was insufficient, some of 

 the ovules increased in size but others remained small. On micro- 

 scopic examination the former showed the remains of a pollen 

 tube, a more or less well developed endosperm, and a number of 

 adventive embryos which seemed to be fully capable of further 

 development. On the other hand, those ovules which had failed 

 to grow showed neither pollen tubes nor endosperm but only the 

 earliest stages in adventive embryony, characterized by the ap- 

 pearance of a few richly protoplasmic nucellar cells. In older 

 stages, such "unpollinated ovules" (i.e., ovules not penetrated by 

 a pollen tube) showed a progressive shrinkage and drying up of 

 their tissues, accompanied by a degeneration of the embryo sac as 

 well as the embryo initials. 



In the second experiment, in which the pistils were treated with 

 pollen from other genera, viz., Hemerocallis, Lilium, Galtonia, and 

 Canna, all of them withered and fell off exactly like unpollinated 

 pistils. 



In the third set of experiments, in which some of the pistils were 

 treated with 1 per cent heteroauxin in lanolin and the controls 

 with pure lanolin, the latter dried up within 4 or 5 days. The 

 auxin-treated pistils, on the other hand, continued to remain at- 

 tached to the plant and three weeks later they showed the presence 

 of young adventive embryos. No endosperm was formed, how- 

 ever, and the embryos seemed to lack the capacity of developing 

 further. 



Although of a preliminary nature, Fagerlind 's observations seem 

 to indicate that in plants showing adventive embryony it is pos- 

 sible to prepare the ovule for the production of adventive embryos 

 by the application of suitable growth hormones, but the real diffi- 



