Feb. i6, 1920 Germination of Barley Pollen 535 



and they then will complete their development. If it is apparent some- 

 time in advance that the desired varieties are not going to flower at the 

 same time, the spikes of the more advanced variety should be removed. 

 This will cause a good development of the secondary culms, which may 

 flower about the time of the later sort. 



The methods developed for the germination of barley pollen appeared 

 to offer advantages which might be used with other species of grasses. 

 Large percentages of germination were obtained with wheat pollen 

 under conditions identical with those used for germination of barley 

 pollen, except that the pollen of wheat was slightly less sensitive to the 



moisture. 



vSUMMARY 



The artificial germinination of pollen of grasses has long been known 

 to be a difficult matter. In a study of the factors affecting viability of 

 barley pollen, its relation to moisture was found to be very delicate. 

 Slight drying caused collapse of the walls, and free moisture caused 

 rapid swelling and bursting. The relation of temperature also is criti- 

 cal. 



Experiments were conducted to determine viability in various solu- 

 tions and in different moist chambers. The former resulted in failures; 

 the latter, in success under delicately controlled conditions. A proper 

 range of humidity must coincide with a certain range of temperature. 



Extensive studies were made of fertilization under field conditions, 

 using pollen in eight successive stages of development, from immature 

 to that obtained two days after dehiscence. Sixty per cent of seed for- 

 mation was obtained when ripe pollen was used. 



The retention of viability by barley pollen when stored under various 

 conditions was studied. Results were determined by artificial germina- 

 tion and by germination on the stigma. No satisfactory results were 

 obtained. 



Study of the conditions governing fertilization in nature shows that 

 conditions unfavorable to fertilizations are also unfavorable to progress 

 in the development of pollen and vice versa. In this way natural fer- 

 tilization is assured. 



LITERATURE CITED 

 (i) Andronescu, Demetrius Ion. 



191 5. THE PHYSIOLOGY OF THE POLLEN OF ZEA MAYS WITH SPECIAL REGARD TO 



VITALITY. 36 p., 4 pi. [Urbana, 111.?] Reference list, p. 36. 



(2) JosT, L. 



1905. ZUR PHYSiOLOGiE DBS POLLENS. In Bcr. Deut. Bot. Gesell., Bd. 23, 

 Heft 10, p. 504-515. Literatur, p. 514-515- 



(3) 



1907. iJBER DIE SELBSTSTERILITAT EINIGER BLUTEN. In Bot. Ztg., Abt. I, 

 Jahrg. 65, Heft 5/6, p. 77-117, pi. i. Literatur, p. 114-117. 



