FERTILIZATION 147 



lination and fertilization (as shown by fusion) was sixty-five to 

 seventy-two hours. Guignard 0G has recorded an interval of two 

 days between pollination and fertilization in Nicotinana Taba- 

 ciini. duel 63 found by artificial pollination that fertilization 

 occurs in Cynomorium four days after pollination, sixteen 

 days after pollination embryos of various sizes being found. 

 Ilofmeister 2 noted the interval as one to three days in 

 Crocus, five days in Arum, from ten days to several months 

 among the Orehidaceae, and in Colchicum autumnale not less 

 than six months (November to May). In the last ease, as is 

 well known, pollination sometimes occurs before there is any 

 appearance of ovules. Miss Benson 10 found three weeks elaps- 

 .ing in Fagus sylvatica between pollination and the entrance of 

 the tube into the embryo-sac, and the same interval is reported 

 by D'Hubert 1T for certain Caetaceae. In Hamamelis virgini- 

 ana Shoemaker ° 2 has found that pollination occurs from Octo- 

 ber to December ; that the tubes develop at onee and grow 

 rapidly until cold weather ; that during January and February 

 the tube may be found safely embedded in the hairy part of the 

 carpel ; and that growth is resumed in the spring, fertilization 

 occurring about the middle of May, five to seven months after 

 pollination. The pollen-grains of Hamamelis show great resist- 

 ance to low temperature, Shoemaker citing cases in which they 

 produced tubes after exposure to a week of cold, the temjiera- 

 tnre sometimes being as low as —15° C. Among the Amentif- 

 erae, however, the interval becomes even more extended. Miss 

 Benson I5 reports that it is one month in Betula alba, two 

 months in Carpinus Betulus, three months in Alnus glutinosa, 

 four months in Corylus Avellana and Quercus Rdbur, and as 

 much as eleven months in certain other oaks ; while in Q. vclu- 

 tina Conrad 36 found the interval between pollination and fer- 

 tilization to be thirteen months. Baillon had long before noted 

 that no indication of ovules is present in Quercus at the time 

 of pollination. Goebel 10 has associated these long intervals 

 with the woody habit, citing Ulmus, Quercus, Fagus, Juglans, 

 Citrus, Aesculus, Acer, Corn us, and Eobinia as illustrations, 

 and stating that the interval is almost a year in American oaks 

 that take two years to ripen their seed. Such cases bear a 

 striking resemblance in this regard to many Gymnosperms. 



A recent study of Monotropa uniflora by Shibata 65 indi- 



