for July, 1920 



243 



Plants That Seldom Fruit 



W. N. CLUTE 



THE common plants of our fields and woods are 

 called sperniatophytes. or seed plants, by the bot- 

 anist, because all normally reproduce by means of 

 seeds, but there is considerable variation in the regular- 

 ity with which such structures are produced and some 

 plants fruit so rarely as scarcely to deserve the name of 

 seed plants. The owner of an orchard, fur instance, is 

 well aware that fruits and their contained seeds can not 

 be counted un in equal numbers every year. There are 

 good years and bad years in the horticulturist's experi- 

 ence, and an in(|uiry into the causes that reduce fruitful- 

 ness is therefore of importance. 



The reason why some plants fail to fruit in certain 

 years is not hard to discern. Unfavorable weather at 

 the time of blooming may blast the blossoms and also 

 the hopes of the orchardist. This is possibly the com- 

 monest cause of the non-fruiting of orchard plants. 

 While perfectly dormant, the buds may endure unharmed 

 temperatures below zero, but when they become flowers 

 they frequently cannot stand even freezing temperatures. 



When a specimen persistently refuses to fruit the con- 

 dition may be due to the fact that it is sterile to its own 

 pollen. j\Iany cases of this kind are known. The trou- 

 ble may be remedied by growing trees of some other 

 variety near the unfruitful specimen. Certain apples, 

 pears, and plums are of this nature and absolutely refuse 

 to bear unless other varieties are at hand to supply the 

 necessary pollen. Still other species are dioecious, that 

 is, the stamens and carpels are produced on separate 

 plants. In such cases, of course, no seeds can be pro- 

 duced unless both individuals are present. This is true 

 of some forms of holly, mulberry, fig and numerous 

 others. The willows and cottonwoods always have dioe- 

 cious flowers. 



Unfavorable weather, far above the freezing tempera- 

 ture, may limit production by preventing the visits of 

 the pollinating insects. A spell of rainy weather, just as 

 the flowers are opening, often greatly reduces the crop. 

 The loss from this source, however, is minimized by the 

 fact that all the blossoms do not open at once, but follow 

 one another for several days and that failing to be pol- 

 linated they may remain open for some time. In the case 

 of some orchids the flowers if not pollinated may remain 

 open for six weeks, but when pollinated they soon wither. 



It is not always unfavorable weather, however, that 

 limits the flower's insect visitors. A scarcity of the in- 

 sect's food while it is in the larval or "worm" stage may 

 make tlie mature insect rare and thus have a direct bear- 

 ing on the crop of fruit. The operations of man are 

 constantly changing the world flora of a region by drain- 

 ing, flooding, burning, ploughing, and the like. If these 

 changes make the food-plant of a species rare, the pol- 

 linating insects that frequent some totally different plant 

 may become rare also. The rarity of some of our native 

 orchids is sometimes attributed to circumstances of this 

 kind. This seldom happens to our common plants for 

 their blossoms are visited by a great variety of insects — 

 often as many as eighty kinds — but there are many other 

 species whose flowers are adapted to the visits of a sin- 

 gle kind of insect and if this insect is absent, no seeds 

 can result. 



One of the most remarkable adjustments of flower and 



insect known is found in the association of the yucca and 

 the yucca moth. The flowers of the yucca are pollinated 

 by tne moth only. The insect, on the other hand, is close- 

 ly dependent upon the plant, for its larv^a; live exclusively 

 upon young yucca seeds. To insure pollination and in- 

 cidentally an abundant supply of seeds for the young 

 moth, the mother insect actually collects pollen and care- 

 fully pollinates the flowers in which she lays her eggs. 

 This is probably the only instance on record where pol- 

 lination is deliberately and intentionally performed by 

 the insect. In other flowers pollination occurs through 

 the effort of insects to get the nectar without though of 

 pollination. The pollen which they bring from one 

 flower is simply brushed from their bodies upon the wait- 

 ing stigmas of another. 



It may also be possible that fruiting is limited by un- 

 usual vegetative activity. Fruiting is a process looking 

 to the preservation of the race by the production of new 

 individuals and may not occur when the plant is thriving. 

 Any shock to the life processes of the plant, however, 

 may stimulate it into fruitfulness. This explains the 

 flowers that sometimes appear on trees that have been 

 struck by lightning, or which have been defoliated by 

 insects earlier in the season. In ancient times such bloom- 

 ing out of season was regarded as the sign of an ap- 

 proaching death in the owner's family, but the death it 

 usually presages is the death of the plant that bears the 

 flowers. The florist takes advantage of the fact men- 

 tioned when he allows his plants to get potbound. Under 

 such circumstances, they commonly produce many flow- 

 ers. In a similar way, the removal of some the new wood 

 in August may induce the formation of flower buds in 

 the peach. The removal of some of the roots has the 

 same effect in other plants. 



Thus far we have been considering the sterility of nor- 

 mally fruitful plants. There still remains, however, ^ 

 number of cases of plants that seldom fruit under even 

 favorable circumstances. The common white or "Irish" 

 ]jotato is a striking instance of this kind. It produces 

 blossoms in abundance and yet the fruit is so rare that 

 many potato growers have never seen it. One could 

 make a long list of such plants. Among the number 

 would be included the sugar cane, the bamboo, sweet po- 

 tato, ground nut (afios), lily of the valley bleeding 

 heart, house leek and some varieties of milkweed. It is 

 likely that some of these fail to produce fruit through 

 some defect in the pollinating mechanism, but in other 

 cases the cause cannot be explained thus. It has been 

 suggested, that failure to set seeds may be due to the fact 

 that the species have various vegetative methods of rapid 

 multiplication. It is ((uite possible that finding such 

 means sufiicient the plants are gradually abandoning re- 

 ])roduction by means of seeds. It is to be observed, 

 liowever. that while seeds and the various devices for 

 nniltiplying the plants vegetatively are alike in producing 

 new plants, they are not (juite alike in function, for the 

 seeds, spread by the wind and other agencies, serve to 

 introduce the species into new regions, while vegetative 

 methods merely multiply the plant once it has gained a 

 roothold there. 



Less government, less legislation, less talk, less playing 

 of the i)olitical game, and more enthusiasm for work and 

 consideration of the .\merican people as a whole is what 

 our statesmen should strive for. 



