stout: pollinations in cichorium intybus 401 



sources was applied to all flowers of each head. In making com- 

 parisons between many such pollinations it is of importance to 

 know if flowers produced on different parts of a plant and at 

 different times in the season are relatively equally productive of 

 seed; the tests reported in tables 15 and 16 seem conclusive that 

 they are sufficiently so for a fair comparison and also that when 

 a low percentage of seed per head is set consistently there is a 

 real condition of partial physiological self- or cross-incompatibility 

 involved. 



OTHER INVESTIGATIONS 



Attention has been given to a study (a) of the requirements for 

 successful artificial germination of the pollen of Cichorium Ijitybus, 

 (b) of the facts regarding the germination of pollen and of the 

 relative rates of growth of the pollen tubes in self- and cross- 

 incompatibility as compared with self- and cross-compatibility, 

 and (c) of the more intricate cytological processes of fertilization 

 and embryo development. 



The artificial germination of the pollen was a special subject of 

 investigation by Dr. Joseph C. Gilman under a scholarship grant 

 from the New York Botanical Garden in the summer of 1913. 

 A large number of experiments were made employing chiefly agar 

 plates and hanging drop methods of culture and using various 

 strengths of various chemical solutions and of the juices of chicory 

 plants. During 191 5 in the studies made by the writer the pistils 

 with pollen in contact were placed on slides and kept in a moist 

 chamber for study. 



On plates of i per cent agar with 25 per cent and 30 per cent 

 sucrose a few tubes developed to a length two or three times the 

 diameter of the pollen, but as the greater number of such tubes 

 burst it is not certain that there was a real germination. Thus 

 far no method of securing artificial germinations more successful 

 than these has been discovered, and until much better germina- 

 tion can readily be secured there is no hope of determining by 

 germination studies whether pollen of different plants shows differ- 

 ences in their physiology. 



Preliminary studies along the other lines indicated above have 



been made and especially of the behavior of the pollen tubes in 



the pistils relative to fertilization, but none of these have at present 



writing reached the stage where they contribute any definite data 



27 



