10 THE WALNUT POLLINATION. 



adheres to the limbs and leaves during the blooming period of the male 

 catkins. The fertilizing power of the pollen is not lost, but is preserved 

 for an indefinite period, and a mere speck falling on the stigma of the 

 female blossom is ample to render it fertile. 



In many instances it has been observed that some trees will produce 

 at times an abundance of flowers of one sex, and few or none of the 

 other sex. Trees — as the walnut — that mature their pollen before the 

 female flowers on the same tree are ready for fertilization, are called by 

 botanists proterandrous; while others, called proterogynous, have their 

 stigmas mature before the pollen is ready. The purpose of this curious 

 functional difference obviously is in favor of cross-fertilization, by pollen, 

 of flowers borne by other trees of the same species. 



According to the Gardener's Chronicle, in 1888, reports became cur- 

 rent of trees in portions of the walnut sections of France bearing a full 

 crop, but the nuts failed to harden, the husks when about half 

 grown withering up, and few good nuts were found. The kernels' which 

 were formed were soft and insipid. Reports made throughout were that 

 "while there were plenty of nuts there was nothing in them," and after 

 assigning different reasons for this failure, conclude "probably from 

 imperfect fertilization of the flowers." Many other similar instances 

 are reported as occurring in different groves. 



* " It is a common occurrence for the walnut to be deficient in producing either the 

 male or female blossoms, which it bears, both of which are essential to its producing 

 and ripening nuts. 1 have a tree, now about twenty years old, which began a few years 

 ago to show blossoms, but those merely female, without one male catkin appearing on 

 the tree, and the consequence has been that after the flowers faded the fruit regularly 

 dropped off. This season, there being a considerable show of female blossoms out no 

 male ones, I thought of trying the plan followed by gardeners in the case of melons and 

 other fruits where fertilization is not freely effected by nature, and having seen abun- 

 dance of male catkins on a tree at a friend's, I asked him to send me some, and he accord- 

 ingly sent me a small paper-bag full, which I dusted and threw over such of the female 

 blossoms as were within my reach. The consequence has been that 1 now have about a 

 dozen fine nuts, swelling out regularly, with every appearance of coming in due time 

 into maturity. All the embryo fruit not fertilized have fallen off as usual. I am 

 pleased with the success of my experiment, and mean, should my tree still prove 

 deficient in male blossoms, with the assistance of my friend's, to supply its wants, and, 

 by taking a little more trouble, I have no doubt I shall be able to render every female 

 blossom fruitful." 



As showing this curious functional difference in our own State, a few 

 facts are cited. A nurseryman at Ventura observed a large seedling 

 walnut tree, which, from its luxuriant growth and symmetrical form, he 

 believed, would be a variety worthy of cultivation. Accordingly, in the 

 spring of 1886, he planted forty pounds of nuts gathered from that tree. 

 When the seedlings bore, none of them produced nuts of any commercial 

 value. This, of course, proved to be a sad disappointment to him, and, , 

 after waiting ten years for a crop, he dug up most of them. Some of the 

 trees had become of large dimensions and had long, spreading branches, 

 and were always quite full of nuts, but without kernels — all hull and 

 shell. This functional difference was investigated; the trees were found 

 to produce an abundance of flowers of the same sex, but few or none of 

 the other, through which imperfect fertilization of the flowers the kernels 

 in the nuts did not form — they were wanting. It is also interesting to note 

 that no attempt was made to correct this curious phenomenon by artificial 

 cross-pollination, by distributing pollen from staminate catkins, or male 

 flowers, of other trees, before digging up the trees. 



*Gardener's Chronicle, London, 1847, p. 541. 



