S44 EXPEKIMENT STATION EECOED. [Vol. 30 



contents of the West Indian as compared with the Mexican and Guatemalan 

 types. Furthermore, the plants of the Guatemalan type are generally con- 

 sidered to be intermediate in hardiness between those of the Mexican and 

 West Indian types, whereas no discernible difference in the freezing point of 

 the sap of the Mexican and Guatemalan types was observed. 



The two groups of varieties of the Hicora pecan and their relation to self- 

 sterility, H. P. Stuckey (Georgia Sta. Bui. 124 {1916), pp. 121-148, figs. 10).— 

 Observations made during a number of years relative to the partial or complete 

 self-sterility of various pecan trees led the author to conclude that there are 

 two distinct groups of varieties of the Hicora pecan. The distinguishing char- 

 acteristics of these groups are described in general, and the differences and 

 some of the characteristics of the two groups as represented by some of the 

 varieties grown on the station grounds in 1915 and 1916 are presented in 

 tabular form. A bibliography of references dealing with sterility in fruits is 

 Included. 



Varieties of one group of pecans here observed shed their pollen at about 

 the same time the majority of the pistillate flowers become receptive, whereas 

 the varieties of the other group shed their first pollen after most of the pistillate 

 flowers pass through the receptive stage. Varieties of both groups produce 

 viable pollen, but varieties of the first group are apt to be self-fertile while 

 those of the second group are apt to be self-sterile. Self-sterility of a variety 

 may be expected in proportion to the interval between the receptive stage of the 

 pistillate flowers and the shedding of the pollen. Mechanical injury to catkins 

 before the date of normal pollen shedding may partially prevent self-sterility 

 among varieties of the second group. Parthenogenesis in pecans is also indi- 

 cated. Phenological data from varieties grown in south Georgia agree fairly 

 closely, as regards the two groups, with that from the varieties at the station. 

 Native hickory trees in the vicinity of the station can be divided into early and 

 late staminate flowering groups, and it appears possible that the hickory will 

 serve as a pollenizer for the pecan. 



The effect of cultural and climatic conditions on the yield and quality of 

 peppermint oil, F. Rabak (U. S. Dept. Agr. Bui. 454 {1916), pp. 16). — In order 

 to obtain data bearing on possible variations in the composition of peppermint 

 oil under varying conditions, plants were grown under various conditions of 

 soil and climate and were harvested at various stages of gi'owth. The oil was 

 distilled from certain parts and also from the entire herb in both the fresh 

 and dry condition and was then subjected to thorough examination. The re- 

 sults are here presented in tabular form and discussed. 



Conditions of soil and climate proved to be influential factors in the forma- 

 tion of peppermint oil and its constituents in the plant. Light sandy or loamy 

 soils appear to be most favorable for the production of an oil of high quality. 

 The yield of oil distilled from fresh plants apparently decreases as the plant 

 matures. Drying the plant before distillation results in a considerable loss of 

 oil. The largest proportion of oil is found in the leaves and flowering tops. 

 On the other hand, the formation of esters and menthol in the oils increases as 

 the plants approach maturity and with drying the plants. The formation of 

 esters and menthol takes place most readily in the leaves and tops. 



The effect of shade upon the peppermint plant is to decrease esterification and 

 the formation of menthol, whereas the action of frost noticeably increases 

 esterification and the formation of menthol. The decrease in the case of shade- 

 grown plants is possibly due to the lessened activity of the elimination of 

 water by the plant. 



