June, 1922 



BETTER FRUIT 



Page Nine 



Pollination of Filbert Varieties 



TN DISCUSSING the question of pol- 

 -'- 1 illation, we will take the term pollina- 

 tion merely to mean the operation which 

 the pollen grain i? placed on the pistil of 

 the female flower. Fertilization is the 

 union of the male and female gametes. 



In considering the pollination of the fil- 

 bert, we find more different difficulties than 

 are connected with any other nut or fruit 

 commercially grown in the Pacific North- 

 west. In addition to being one of the group 

 that depends on the wind for pollination, 

 the filbert blooms during that part of the 

 vear which is not usually considered ideal 

 blooming time. The filbert ordinarily 

 blooms during the rainy season, or the 

 period during which rains are more or less 

 common. 



Insects are not essential for cross-pollina- 

 tion as with other fruits. The pollen being 

 borne in separate flowers, is carried to the 

 pistillate flowers by the wind. Being of 

 a nature that rapidly absorbs water, the 

 pollen grain cannot be disseminated except 

 during those periods or times of the day 

 when the moisture is least prevalent. Wet 

 pollen cannot be blown or scattered about 

 by the wind. 



The catkins are formed during the late 

 summer and held on the tree until January 

 and February, when the pollen is shed. 

 Each catkin contains, on the average, about 

 150 bracts and in each of these we found 

 about 8 anthers. Figuring that 1000 pollen 

 grains are found to the average anther, we 

 see that there is possibility of over a million 

 pollen grains being produced by one catkin. 

 It gives a great abundance of pollen, but 

 this is necessary when we consider the 

 possibility of the floating pollen grains 

 lighting on the small individual pistillate 

 flowers. 



The pistillate flowers are contained in 

 separate buds and are not evident until con- 

 siderably later than the first catkin appear. 

 With the earliest varieties we find the first 

 appearance of the pistillate flowers to be 

 around the end of November or the first 

 of December, while some varieties do not 

 appear for some weeks after that. Although 

 the earlier varieties show the pistils the first 

 part of December, the full growth is 

 usually not made until the latter part of 

 January and February. In each bud we 

 find from nine to ten pistils, or separate 

 female flowers. From each of these there 

 is a possibility of developing a single filbert 

 so that we find large clusters of nuts where 

 the pistils have been well pollinated. 



After a pollen grain is placed on a pistil 

 it begins to germinate almost immediatelv 

 and makes a growth down into the tissue 

 of the pistil. .After growing a short distance 

 mto the pistil the nucleus encysts and re- 

 mains in this state for from four to five 



By C. E. Schuster, 



Oregon Agricultural College, Corvallis 



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I Filbert culture is a comfaratiz'ely | 



I iiezv branch of nut growing in this | 



I country. Little has been written on \ 



I the subject and there is much yet to | 



I be learned. Professor Schuster tnade | 



I a distinct afid z'aluable contribution | 



I to existing funds of information | 



I about the filbert in studies of its | 



I follination habits fursued last year. \ 



I His discoveries, as reported to the | 



I annual convention of nut growers, | 



I may see?n a bit technical . T hey are \ 



I qttite understandable, as a matter of \ 



I fact, and foint out tnethods of flant- | 



I ing that seem of vital importance | 



I to everyone who undertakes filbert | 



i growing in the Pacific Northwest. | 



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months. At the end of this period the 

 growth is continued and the fertilization 

 takes place. 



From now on we will make no further 

 mention of this question of fertilization. 

 This then gives us a condition where pol- 

 lination occurs on an immature pistil or un- 

 developed female organ and the male 

 gamete, or nucleus of the pollen grain, is 

 forced to wait for the development of the 

 female part or gamete. 



Usually the pistillate flowers of the 

 main varieties are out and fully developed 

 before the catkins begin shedding the 

 pollen. But, since it is well known that 

 the different varieties produce pollen at 

 different periods, we often have the con- 

 dition of pollen from a variety falling upon 

 the pistil of another variety before the 

 pistils have developed their full growth. 

 The exact state of receptivity of the pistil 



C.-itkins and Pistillate flowers of filltcrt ai 

 blooming time. 



is not known, but on February 3, 1 92 1, a 

 number of blossoms were hand-pollinated. 

 At this stage the pistils were a little more 

 than through the bud scales and it was two 

 weeks before they were considered fully 

 developed and in fine condition to receive 

 the pollen. 



SEVERAL varieties were used for cross- 

 pollination at this time. With the 

 varieties that gave good results when used 

 for cross-pollination at the later time, at 

 which the pistils were fully developed, 

 practically the same results were obtained 

 with early pollination. In other words, 

 the pistils were receptive shortly after mak- 

 ing their appearance, and will not reject 

 the pollen before they reach a state of 

 maturity. 



With the blossoming season coming dur- 

 ing January and February what insi'rancc 

 have we against rainy weather at this time? 

 Pollen being light and blown about by the 

 \vlnd, it stands to reason that rain is detri- 

 mental to its distribution. So means of 

 circumventing these rains must be con- 

 sidered. 



In the first place, the blooming season 

 of the catkins, or male flowers, is long, 

 considering other fruits. Not all the pol- 

 len is mature at one time. The develop- 

 ment of the catkin is progressive from the 

 upper end to the lower part and is rapidly 

 increased by warm temperature. With the 

 progressive development and cool temper- 

 ature at this time of the year, the shedding 

 of the pollen is thus spread over a relatively 

 long period. 



Pollen is viable over considerable periods. 

 As it is first shed it gives a high test of 

 germination, decreasing at a rate of about 

 one per cent per day for the first fifteen 

 d.iys and decreasing more rapidly after this, 

 so that by the end of thirty days it is 

 down to about 25 per cent viability. Thus, 

 the catJcins may mature and hold the pollen 

 for some considerable time without any 

 material dam.ige to the pollen. 



As the pollen is matured the anthers con- 

 taining the pollen are split open, allowing 

 the pollen to escape. If the time of ma- 

 turity comes during a period of high 

 humidity the walls of the catkins absorb so 

 much moisture that it forces the sections 

 together so opening cannot take place until 

 the anther is partially dried out. If the 

 anther should open and the catkin be 

 moistened this same process or condition 

 forces the halves of the anther together .so 

 the washing of the pollen from the catkin 

 is partially prevented and the anther is able 

 to hold the pollen until favorable weather 

 conditions are at hand. 



Tests at the e.xperim.ent station show 

 that the pollen is very resistant to atnio- 



