292 



other variety was necessary for this. This would explain the observed 

 sterility in large fruit orchards composed of a single variety. 



Ewert^ acknowledges that self-sterility has been determined for many 

 species, but is of the opinion, nevertheless, that large plantations of only one 

 variety do not fall behind those made up of mixed varieties, because cross- 

 pollination will be secured promptly by honey and bumble bees. The setting 

 of the fruit fails only if, because of unfavorable weather, the insects are 

 unable to fly. 



According to our theory there should also be noted in this connection 

 the alternation between chasmogamic flowers (sterile with large petals), 

 and cleistogamous flowers (fertile with aborted petals). With E. Loew", 

 we perceive in these conditions no mutations in de Wies' sense, but simple 

 variations which depend on the form of nutrition. Goebel found that 

 cleistogamous flowers formed earlier and he was able, by keeping them 

 dry and exposed to abundant sunshine, to force violets which had previously 

 borne cleistogamous flowers, to form chasmogamic blossoms in July, which 

 is a very unusual occurrence at that time of year. The alternation was 

 called forth by the postponement of the use of the plastic food material at 

 hand. The cleistogamous bud cannot develop with a lack of moisture and 

 abundance of light and the plastic building materials then remain at the 

 disposal of later produced blossoms. Since in these the pistils are rarely 

 formed and do not mature, the material is free for the especially vigorous 

 development of the petals which need the light. 



Seedless Fruits. 



Sterility is often connected with the appearance of seedless fruits, and 

 can in the same way become a peculiarity of the variety. 



In a new American variety of apples (the "Wonder of Horticulture") 

 this charactistic has recently been considered an especial recommendation 

 of the variety', since the blossoms yield fruit without having been fertilized. 

 In this way, the harmful agents threatening other varieties at the time of 

 blossoming, such as frost, mist, rain, drought, poor insect pollination, etc., 

 are avoided. The new variety has no corolla and to this fact is attached the 

 hope that blossom pests and other insects, which would be attracted by the 

 petals, may spare such flowers. 



Seedless varieties of fruits, i. e., those in which poorly matured seeds 

 are found, have been known from the earliest times as, for example, the pear 

 "Rihas Seedless," ("Rihas Kernlose") and the Seedless Father Apple 

 ("Vaterapfel ohne Kern") It is said that it frequently happens that vari- 

 eties free from seeds appear from grape seedlings, unfortunately dis- 

 tinguished, however, by their small size and the great hardness of the 

 grapes. 



1 Ewert, Welche Erfahrungen sind gemacht in bezug auf g-eringere Frucht- 

 baxkeit, etc. Proskauer Obstbau-Zeitung, 1902. 



2 Loew, E., Bemerkungen zu W. Burck's Abhandlung uber die Mutation als 

 Ursache der Kleistogamie. Biol. Centralbl. XXVI, 1906, Nos. 5-7. 



3 Janson, A-, Der kernlose Apfel. Gartenflora, 1905, p. 490. 



