MISSISSIPPI EXPERIMENT STATION. 47 



From the foregoing discussion and tables it is to be seen that the 

 external characters of the Radish x Kohlrabi hybrid are 62.2% like 

 the Radish parent and 37.8<;'(, like the Kohlrabi parent. The micro- 

 scopical characters show 54.79o Radish characters and 45.3% Kohlrabi. 

 The relationship here between external and microscopical characters 

 is not so close as in the other hybrids discussed, still the difference is 

 not ver\- great, being less than 8%, and the parent dominant in one set 

 of characters is dominant in the other also. The pistillate parent had 

 complete dominance over four of the external characters and one of 

 the microscopical; the staminate parent had pure dominance over one 

 external character and two internal. Of the sixteen external characters 

 here considered, five show complete dominance; three of the twenty- 

 five microscopical characters show dominance. Here as in the case of 

 the other hybrids discussed, the great majority of the characters are 

 intermediate, yet the percentage is not so high. 



Other Hybrids. 



In addition to the hybrids already mentioned, the structure of 

 certain others was studied briefly. Among these hybrids were Salix 

 cordata x S. Candida, Citrus trifoliata x C. aurantium, var. dulcis, 

 Marshall strawberry x Crescent strawberry. Calceolaria hybrida x C. 

 integrifolia, and Wild Goose Plum x Troth's Early Peach. 



Salix Hybrids. Structure of lea^'cs, twigs and fruit of the Salix 

 hybrid was studied. The most interesting characters noted were as fol- 

 lows : Salix cordata has six rows of bast fibers, S. Candida three and the 

 hybrid three. Differences were noted in the form and size of certain 

 cells of the embryo of the three plants, but since the plants were open 

 fertilized the parentage of the embryos is not certain. 



Citros Hybrids. The structure of the fruit of several Citrus 

 hybrids was studied. These hybrids were the result of duplicate and 

 reciprocal crosses between Citrus trifoliata and C. aurantium, var. dul- 

 cis, and were produced by Dr. H. J. Webber of the U. S. Department of 

 Agriculture. (For full description of the parents, see Cyclopedia of 

 Horticulture, Vol. I, by L. H. Bailey, and for description of the hybrids 

 see Year-book of Department of Agriculture for 1904, 1905 and 1906.) 



The peel of these fruits proved most satisfactory for the comparison 

 of structure. In Citrus aiu-antium, var. dulcis, the peel is 5 - 'J mm. 

 thick on ripe fruit; in C. trifoliata, it is 2 - 4 mm. thick; on the hybrids it 

 varies considerably, being 3 - 5 mm. thick in Rusk citrange, 4 - 6 mm. 

 in Willit's citrange, 4 - 6 mm. in Citrange 767, 3 - 6 mm. in Citrange 775, 

 4.5-6.5 mm. in Citrange 783, 4-5 mm. in Morton citrange, and 

 3.5-5 mm. in Citrange 761. The hybrids are intermediate in this 

 character, but nearer the female parent in most cases. Citrus auran- 

 tium, the sweet orange, was the female parent in all crosses, except in 

 the Rusk citrange. 



The epidermal cells of the peel were 27m long in the Citrus trifoliata, 

 and 15m long in C. aurantium. The hybrids were all intermediate but 

 nearer the sweet orange parent. No difference was to be noted in the 

 reciprocal crosses in regard to this character. The outer wall of the 



