Detlefsen and Ruth : Chestnut Hybrids 



313 



a single season. The vigorous growth 

 of the hybrids is shown by their hav- 

 ing a spread of over forty-five feet, 

 while the American sweet and the 

 Japanese parents measured about thir- 

 ty and sixteen feet, respectively. 



The Second Generation 



The first generation hybrids, par- 

 ticularly the Boone with its vigorous 

 growth, early maturity, and with an 

 abundance of nuts of excellent quality 

 and large size aroused Mr. Endicott's 

 interest to such an extent that he 

 planted over 175 seedlings from this 

 particular hybrid tree. A first plant- 

 ing of twenty-five second generation 

 seedlings was made in 1906, and a 

 second planting of over 150 was made 

 in 1909. All of these are undoubted- 

 ly genuine second generation hybrids, 

 because the three first generation 

 trees were quite isolated in a field al- 

 most a mile from the nearest Amer- 

 ican sweet. While all the second gen- 

 eration hybrids were grown from the 

 Boone nuts, it is of course possible 

 that the male parent was occasionally 

 either Blair or Riehl, since the three 

 trees were planted in a row and spaced 

 about one hundred yards apart. This 

 does not vitiate our Mendelian ex- 

 periment, for in any event the second 

 generation trees came from the first 

 generation mated interse, and prob- 

 ably all or nearly all of them ac- 

 tually came from the self-fertilized 

 Boone hybrid. 



In perpetuating the Boone chestnut, 

 by growing a second generation, Mr. 

 Endicott had hoped to see a fairly 

 constant repetition of the excellent 

 qualities of his first three hybrids, 

 namely three large nuts of good color 

 and quality with little tomentum, ly- 

 ing free in the burr, and a vigorous 

 heavy yielding tree. Of course, he 

 was doomed to disappointment in this 

 respect, because the most pronounced 

 segregation was inevitably predeter- 

 mined. The second generation trees 

 v/ere very uneven in growth and size. 

 The smallest was hardly more than 

 eight feet high, while the largest was 



about twenty feet high, when they 

 both were fourteen years old (Fig. 8). 

 None of the trees showed the ex- 

 treme vigor or precocity or heavy- 

 bearing qualities characteristic of the 

 first generation. While the original 

 Boone tree bore its first nuts at sev- 

 enteen months, the second generation 

 Boone trees were from five to nine 

 years old before bearing; this range 

 almost covers the difference between 

 the original Japanese and American 

 sweet parents. The time of ripening 

 also showed wide variation, since it 

 overlapped both parents. In 1920, for 

 example, the second generation trees 

 ripened their nuts from the first week 

 in September through the middle of 

 October. 



In size of nuts the trees showed un- 

 mistakable segregation. The nuts of 

 the original hybrid were intermediate 

 between both parents, but these trees 

 gave a greatly increased range of 

 sizes (Fig. ii). Some were as small 

 as the American sweet, and all grades 

 were found up to forms larger than 

 the first generation Boone and almost 

 as large as the Japanese. The amount 

 of tomentum was intermediate in the 

 first generation, and showed a great 

 range in the second. Almost any 

 size nut could be found with any de- 

 gree of tomentum. The first two and 

 last two F" nuts in Fig. 1 1 illustrate 

 this point. W'hile the nuts on different 

 trees showed a great range of varia- 

 tion in size, form and tomentum, the 

 nuts on any individual tree were re- 

 markably uniform. Figure g shows 

 two groups of these second genera- 

 tion nuts. Each group, coming from 

 a single tree, is uniform within itself, 

 but one group gives consistently larg- 

 er nuts, with slightly more tomentum. 



Most of the trees gave three nuts 

 to a burr, but some gave only one 

 nut with two aborted nuts like the 

 Japanese parent (Fig. 13), and others 

 gave as many as eight nuts in a burr 

 (Fig. 10). W'hen a tree produced 

 singles these were often ovoid or 

 acorn-shaped (Fig. 12). While all 

 three of the original hybrid trees pro- 



