HORTICULTURE. 533 



The general conclusiou is reached that the question of carbon nutrition is 

 of great importance in plant culture and should be widely investigated. From 

 his investigations as a whole, the author is of the opinion that the increaseil 

 flower development under carbonic acid treatment is due to a certain excess of 

 carbohydrates over the soil nutrients. The fact that 0.03 per cent of carbonic 

 acid has usually been considered as sufficient for plant growth is attributed to 

 the failure to conduct investigations in the presence of a sufficient amount of 

 light for the greater utilization of carbonic acid. 



Another hypothesis to account for Dr. Swingle's experiments with citrus, 

 A. C. and A. L. IIagedoorn {Amer. Nat., 48 (1914), No. 511, pp. U6-U8).— The 

 authors advance the hypothesis that Citrus trifoliata, the lemon, orange, and 

 other citrus fruits used in Swingle's cross-breeding experiments (E. S. R., 29, 

 p. 839) are self-sterile and that the seeds, normally produced, are produced 

 asexually with a resulting trueness to type. Likewise, although the plants 

 secured from a first cross differ exceedingly among themselves, these new 

 forms reproduce only their own kind because they normally produce seed 

 asexually. 



The authors have begun an experiment with squashes to find out whether 

 it is possible that a plant impure for a number of genes produces a variable F2 

 generation of only completely homozygous plants. Certain hybrid plants in 

 which the female buds have been carefully sealed have pi'oduced no fruit; 

 others have produced plenty of empty fruit ; and still others have produced 

 several fruits full of viable seed. These seeds are to be grown with a view 

 to studying the F2 generation. 



Fertilizer experiments with, muskmelons, J. W. Lloyd {Illinois Sta. Bui. 

 155, Ahs. (1912), pp. Jf, figs. 2). — A summarized account of experiments previ- 

 ously noted (E. S. U.. 28. p. 40). 



Onion culture on muck lands, C. P. Halligan (Michigan Sta. Spec. Bui. 67 

 (1914), PP- S-18, figs. 12). — A practical treatise on onion culture with special 

 reference to muck lands. It discusses the drainage and preparation of soils, 

 various cultural operations, harvesting, storing, and varieties. 



Spray and practice outline for 1914, H. J. Eustace and R. H. Pettit 

 (Michigan Sta. Spec. Bui. 69 (1914), pp. 24, figs. 7). — This bulletin contains 

 general spraying directions for the treatment of orchard and small fruits and of 

 vegetables. 



The relation of ventilation to the keeping qualities of fruits and vege- 

 tables, G. R. Hill, Jr. (Wash. UniA:. [St. Louis] Studies, 1 (1913), I, No. 1, pp. 

 46-64). — A report on the author's experimental studies on the respiration of 

 fruits and growing plant tissues, the substance of which has been largely noted 

 from another source (E. S. R., 29, p. 538). In addition to the work with fruits, 

 the present paper contains some additional data on the keeping qualities of 

 lettuce with good ventilation, and with no ventilation in air, in nitrogen, and 

 in carbon dioxid. 



Methods of heating commercial greenhouses, C. Pynaert (Jour. Soc. Nat. 

 Hort. France, 4- ser., 15 (1914), May, pp. 336-348, pi. 1). — A descriptive account 

 of various greenhouse heating systems, including the results obtained the first 

 winter from a steam plant installed in a greenhouse establishment in Ghent. 



The status of fruit culture in Tunis and Algeria, L. Guillochon (Bui. Dir. 

 G6n. Agr. Com. et Colon. Tunis, 18 (1914), Nos. 14, pp. 87-103; 76, pp. 219- 

 241)- — This embraces the results of a general survey of the fruit industry in 

 various parts of Tunis and Algeria. 



The blooming time of fruit trees, J. P. M. Cam man (Maandbl. Nederland. 

 Pomol. Ver., 4 (1914), No. 5, pp. 94-99). — Data for the beginning and end of the 

 blooming period are given for numerous varieties of apples and pears growing 



