Tukey • Horticulture is a Great Green Carpet that Covers the Earth 155 



standing of plants and how they grow, 

 which is as though they had become a 

 part of the plant and were able to 

 thread their way in and about it as 

 easily and with as much understanding 

 as they would their own homes. Some 

 people have dubbed this "experience," 

 "common sense," or the "green 

 thumb." 



And while all of this is fine, there 

 are not enough craftsmen with the 

 green thumb to satisfy all needs. Fur- 

 ther, while the green thumb may have 

 its virtues, it may also have its faults. 

 And so, sooner or later, we invariably 

 turn to some system whereby the art 

 and the folklore of a subject may be- 

 come tested, rationalized, and cata- 

 logued, so that it can be handed to a 

 great number of men for use. This is 

 particularly so in America, where the 

 exactitudes of conquering and subduing 

 a Continent have left little opportunity 

 for some of the qualities which only 

 time provides. The tendency in Amer- 

 ica has been to work as much as pos- 

 sible, therefore, by rules and handbooks 

 and charts and tables as the engineer 

 would do when he builds a bridge, so 

 as to remove the guess work and the 

 gamble. 



From this has come a sort of "bio- 

 logical engineering," or in our case 

 "horticultural engineering." It is all 

 based on research and the research 

 method, which is essentially a careful 

 or critical search for knowledge, par- 

 ticipated in and enjoyed by many- 

 trained scientists, professional horticul- 

 turists, fruit growers, and amateurs 

 alike. 



Scientific plant breeding.— Hap- 

 pily, there is already a good start to- 

 ward "horticultural engineering." The 

 creation of improved varieties of horti- 

 cultural plants by scientific breeding 

 methods is an example. In the past left 

 largely to chance, new varieties are now 

 made to order for particular needs. The 

 hardy chrysanthemums from Chicago, 



the h\brid onions from the U. S. De- 

 partment of Agriculture, the Great 

 Lakes lettuce from Michigan, the im- 

 proved Pascal-types of celery from Cor- 

 nell, the disease-resistant cabbage from 

 Wisconsin, the V-peachcs from Can- 

 ada, the Cortland apple, the Stanlc\- 

 plum, and the Catskill strawberry from 

 New York, the series of Haven peaches 

 from Michigan, the Shasta and Lasher 

 strawberries from California, the La- 

 tham red raspberry from Minnesota, 

 the Blakemore strawberrv from Louisi- 

 ana—these are all products of scien- 

 tific plant breeding. 



Chimaeras, polyploidyy and plant 

 breeding.— The scientist has learned 

 that many fruits are truly monstrosities, 

 or chimaeras as they are properly called. 

 Some bud sports, many variegations, 

 and such odd fruits as the Sweet-and- 

 Sour variety of apple, with one por- 

 tion sweet and an adjacent portion 

 sour, are now explained as chimaeral, 

 and composed of a mixture of tissues 

 of varying genetic make-up— not the 

 uniform, solid, simple creation we have 

 often surmised. 



Basically, most plants are diploids, 

 that is, thev have two identical sets of 

 chromosomes in each cell. The rasp- 

 berry', for example, has two sets of 

 seven chromosomes— a total of four- 

 teen. Plants with more than two sets 

 of chromosomes are called polyploids. 

 Specificalh', if they have two sets they 

 are diploids; if three sets, triploids; if 

 four sets, tetraploids— and so on. 



Many polyploids have arisen in 

 nature during thousands and thousands 

 of years by chance doubling of chromo- 

 somes. From these, man has selected 

 many desirable forms for cultivation, 

 which are now the varieties of com- 

 merce. The cultivated strawberry is an 

 octoploid, with eight sets of chromo- 

 somes; and the blackberry ranges from 

 diploid to twelve-ploid. 



The thomless blackberry^ is found 

 to consist of a layer of thomless tissue 



