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FLORIDA STATE HORTICULTURAL SOCIETY 



clonal variety arises because its flowers 

 are imperfect and do not supply viable 

 pollen suitable for any sort of fertilization. 

 In certain cases, as for some varieties 

 of Strawberries, an examination shows 

 the absence of stamens. In other cases the 

 stamens may be present, and may shed 

 pollen, but adequate examination under 

 a microscope together with tests for via- 

 bility will readily reveal the impotent con- 

 dition of the pollen. 



ADAPTATIONS LIMITING SELF- AND 

 CLOSE-POLLINATION 



The mention of adaptations for cross- 

 pollination naturally brings to mind the 

 many varied and marvellous structural 

 adaptations for "cross-pollinations" by in- 

 sects. But no matter how complex these 

 may be, as long as the flowers of the dif- 

 ferent individuals of a species are alike 

 and as long as there are numerous flowers 

 open on a plant at the same time structur- 

 al adaptations of themselves do not pre- 

 vent close-pollination (from flower to 

 flower on the same plant or from plant to 

 plant of a clonal variety.) 



To take a seed-grown variety to il- 

 lustrate this point, it is mechanically as 

 easy for a bumble bee to carry pollen from 

 the stamens of a flower on a Red Clover 

 plant to the pistil of another flower on that 

 same plant as it is to carry such pollen 

 to a flower of another plant and the 

 chances for doing so are greater. Adaj)- 

 tations which limit self-pollination do not 

 necessarily restrict close-pollination. In 

 such cases the agent effecting close-pol- 

 lination becomes an important factor in 

 pollination, but the planting in solid blocks 

 of such a clonal variety does not compli- 



cate or limit the possibility of the action 

 of this agent. With the adequate opera- 

 tion of the insects, either a single plant of 

 the Red Clover, or a solid block planting 

 with one clone of the Red Clover, or a 

 planting with every plant a different seed- 

 ling would be pollinated equally well. 

 Without any action of insects there would 

 be the same restriction in fruit setting, 

 provided, of course, that the factor de-- 

 ciding the setting of fruit is solely that 

 of pollination. 



But structural adaptations may advance 

 in complexity until close-pollination is al- 

 so restricted. In certain Primulas, Lyth- 

 rums, and Orchids there are different 

 forms of flowers for individuals or for 

 groups of plants. These are such that it 

 is mechanically easier for insects to effect 

 certain "legitimate" cross-pollinations. In 

 such cases the exclusive growing of a 

 clone having one form of flower tends to 

 reduce pollination. It appears, however, 

 that such a specialization does not exist 

 to a marked degree in any of the impor- 

 tant fruit crops at least in those grown 

 in temperate regions or that have perfect 

 flowers. 



What has just been said regarding 

 structural adaptations for cross-pollina- 

 tions applies as well to those adaptations 

 in which the pistils and stamens in indivi- 

 dual flowers mature at different times 

 (condition called dichogamy). In most 

 plants, dichogamy prevents self-pollina- 

 tion but not close-pollination. Thus in 

 the single-flowered types of the garden 

 Geraniums the stamens of a flower shed 

 j)ollcn considerably in advance of the ma- 

 turity of the pistil of that flower. But 

 tJKTf art' nsualiv llowcrs of various ages 



