THE PLUM IN KANSAS. 95 



instances of the beneficial effect of cross-fertilization, but, reading 

 between the lines, as many or more instances of the failure of good 

 results from cross-fertilization have been recorded. Cross-fertiliza- 

 tion, therefore, unless it be effected in the direction of the natural 

 affinities of the varieties, does not completely explain why certain 

 varieties, even with the aid of cross-pollination, may be prolific one 

 season and the next produce no fruit at all ; why one season the 

 fruit will be large and fine, the next inferior in size and quality ; why 

 an unusually fine variety in the woods and thickets will be worthless 

 when removed from its surroundings, even with subsequent best of 

 care and culture. 



About ten years ago I began making artificial crosses for the pur- 

 pose of breeding improved varieties. My grounds contained at least 

 200 trees, mostly selected from the woods and thickets along the 

 Minnesota and Cottonwood river bottoms, together with a few hor- 

 ticultural varieties of P. americana. I soon found that many of 

 my desired crosses were difficult to obtain. I observed numerous 

 adaptations to ensure cross-pollination, together with differences in 

 morphology of the stamen and pistil. Crosses between certain forms 

 were fully fertile, while with others negative results were invariably 

 obtained. Reciprocal crosses between varieties and between species 

 were not equally fertile. I determined to go into the matter system- 

 atically, keeping a careful record of each cross made and noting the 

 result, raising hundreds of seedlings and again experimenting with 

 them. 



P. americana and other species of Prunus vary much in their 

 wild state in flower, fruit, foliage, season of maturity, and other 

 botanical characteristics, so much so that an enterprising botanist 

 might easily pick up in the thickets of almost any natural area where 

 they abound a dozen or more varieties with characters so distinct 

 from the type as to entitle them to the distinction of specific varieties. 

 The writer has no desire to inflict upon scientific botany any further 

 division of the botanical characters of a species which is already 

 sufficiently defined, but only offers his classification for the purposes 

 of this pajDer in the interest of economic horticulture. 



CLASSIFICATION. 



Adopting the nomenclature used by Darwin in his "Different 

 Forms of Flowers on Plants of the Same Species," and classifying as 

 to morphology and function, we find the following fairly well-defined 

 forms in addition to the hermaphrodite form of botanists : 



Dichogamous Group. — Proterogynous, on which the stigma is ready 

 for fertilization and has passed the receptive stage before the pollen 

 matures. Proterandrous, on which the pollen ripens and matures be- 

 fore the stigma is ready for fertilization. 



