293 



The production of seedless fruits is mentioned often in the more recent 

 works. Kirchner^ who also cites Waite's" observations, declares that 

 typically and normally developed fruits are obtained only by crossing with 

 the pollen of a different variety. The largest fruits are always produced by 

 cross-pollination. Pears produced by self-pollination developed at times 

 almost no seeds. The flowers exposed to the visits of bees, or artificially 

 cross-pollinated, on the contrary, yielded fruit with abundant healthy seeds. 

 Thus it would be advisable to grow a mixture of varieties. 



In opposition to this theory, Ewert', even in his latest papers, holds to 

 his point of view, advocating for practical reasons the cultivation of a 

 single variety in blocks. 



In regard to seedless grapes, we will refer to the investigations of 

 Miiller-Thurgau*. Ewert emphasizes, in reference to seed-bearing fruits 

 that, for the setting of the fruit, the amount of organic material at 

 the disposal of the individual blossoms is of especial importance. In various 

 cases a better nutritive condition for the individual blossoms can be obtained 

 artificially by ringing, since they vary in their development. The pistils 

 are either greatly developed and project as much as one centimeter above 

 the anthers (protogyny), or both sexual organs are equally long (homog- 

 any), or the pistils are shorter than the stamens (protandry). Ewert's 

 experiments do not confirm absolutely the conclusion that the stronger pro- 

 togny is developed, the more the blossom, which is consequently self-sterile, 

 demands the pollen of some other variety, and, conversely, the more homog- 

 any and protandry manifest themselves, the greater the possibiUty of self- 

 pollination. It is evident that the organic nutriment is carried first of all to 

 those fruit buds, in which cross-pollination has made seed formation possible. 

 In comparing fruits containing seeds and those without seeds on the same 

 tree, the seedless ones are smaller and are often malformed. If seedless fruits 

 alone are produced on a tree, by keeping away all foreign pollen, they attain 

 the same size as do those bearing seeds. Probably fruits can also be pro- 

 duced without the action of pollen. 



In some cases fruits can be observed in which the core does not exist, 

 or is scarcely indicated. In reference to the former, Burbidge^ reports that 

 pears without seeds and core represent very sohd parenchymatous fruits, 

 said to be larger, better flavored and possessing a better keeping quality 

 than pears containing seeds. 



I, myself, some years ago, received a branch of pears, one specimen of 

 which is given half-size in Fig. 36. The fruits were perfectly hard and 



1 Kirchner, O., Das Bliihen und die Befruchtung der Obstbaume. Vortrag. Ref. 

 Zeitschr. f. Pflanzenkrankh. 11)00, p. 297. 



2 Waite, Merton B., The pollination of the pear flowers. Washington, 1894, 

 U. S. Dept. Agric. Bull. 5. 



3 Ewert, Bliitenbiologie und Tragbarkeit unserer Obstbaume. Lrandwirtsch. 

 Jahrbucher, 1906, p. 259. 



4 Muller-Thurgau, Folgen der Bestiiubung bei Obst- und Rebenbliiten VIII. 

 Ber. d. Zuricher Bot. Ges. 1900-1903. 



5 Royal Horticultural Society of London. Cit. Bot, Centralbl. 1881. Vol. VIII, 

 p. 319. 



