HORTICULTURE. 437 



On the root development of fruit trees, K. Kroemer (Ber. K. Lehranst. 

 Wein, Obst u. Gartenbau Geisenheim, 1911, pp. 162-170; Landw. Jahrb., ^3 

 (1912), Ergdnsungsh. 1). — A discussion of this subject based ou investigations 

 conducted at the plant physiological experiment station at Geisenheim. 



Investigations on the g'ermination of pollen of fruit trees, A. Manaresi 

 {Staz. Sper. Agr. Ital., 45 {1912), No. 11, pp. 809-873).— The studies here re- 

 ported were conducted during the 3 seasons, 1910 to 1912. The pollen was secured 

 from fruit blossoms of various species and germinated principally in sugar solu- 

 tions. Among the objects of the investigations was an attempt to define the 

 action of stigmas reported by Richer, who found that many kinds of pollen 

 which could not be made to germinate either in water or sugar solutions readily 

 sent out their pollen tubes when fragments of stigmas of the same or nearly 

 related species were added to the cultures (E. S. R., 14, p. 1046). Studies were 

 also made of the best conditions for germinating pollen in artificial cultures and 

 of diverse germinating power among different varieties. The author's results 

 are presented in a series of tables and discussed. 



It is concluded from the investigations that the presence of pieces of fresh 

 stigmas in the culture results in a greater rapidity of germination and of growth 

 in the pollen tube and also in a greater germination of the pollen itself. If the 

 fragments are not fresh, on the other hand, germination may be either retard- 

 ed or prevented. Fresh stigmas of another variety or of another species are 

 preferable to dried stigmas of the same kind as the pollen. The author is 

 unable to explain the nature of this action of the stigma on the pollen, although 

 it is suggested that it may be due to the secretion of one or more substances 

 which stimulate the pollen. Stigmas which were immersed in water from 15 

 minutes to 16 hours still exerted a more or less favorable action on germination. 



The author found a 10 to 15 per cent saccharose solution satisfactory for the 

 majority of cases, although some pollens germinate well in a 30 per cent solu- 

 tion. The best germination temperature appears to range around 15° C. With 

 average conditions germination is completed in from 6 to 12 hours. Strongly 

 concentrated solutions retard germination. 



Pollen germination was quite variable not only between species but between 

 varieties. Germination in any one year was fairly constant between diffei'ent 

 plants of the same variety, which leads the author to conclude that good or 

 poor pollen germination in a sugar solution is a varietal characteristic. Pollen 

 from vigorous trees germinated better than pollen from diseased trees. 



A bibliography of pollination literature is given. 



The frost resistance of apricot and peach pollen, R. Ewert (Ber. K. 

 Lehranst. Olist u. Oartenbau Proskau, 1911, pp. 83-85, in Landio. Jahrb., 43 

 (1912), Ergdnzungsl). 1). — In the author's experiments, here briefly noted, sev- 

 eral samples of pollen from apricot and peach blossoms were submitted to tem- 

 peratures ranging from —8 to — 15° C. for periods of from 2 to 3 hours. The 

 results, although not uniform, indicate that both apricot and peach pollen have 

 a relatively high resistance to cold. 



Factors infl.uencing the formation of fruit buds in apple trees, B. S. 

 Pickett {Trans. Mass. Hort. Soc, 1913, pt. 1, pp. 57-72).— This is largely a 

 review of experiment station literature on the subject. 



The fertilization of apple orchards, J. P. Stewart {Pennsylvania Sta. Bui. 

 121, pp. 3-28, pis. 4, figs. 2). — This bulletin reviews the more practical results 

 of the author's orchard fertilizer investigations (E. S. R., 28, p. 143) and also 

 contains data on the fifth year's experiments in some of the orchards. It largely 

 displaces Bulletin 100 of the station (E. S. R., 23, p. 341). 



In the experiments as a whole it has been found that variations in fertiliza- 

 tion alone have resulted in average differences ranging from 50 to 460 bu. per 



