AGRICULTURAL BOTANY. 729 



the facts of plant nutrition and in all probability the heterotrophic nutrition 

 sugjiested by the author's experiments is to some extent effective. 



Biolog'ical and toxicological studies upon Penicillium puberulum, C. L. Als- 

 BKBG and O. F. Black {Proc. Soc. Expt. Biol, and Med., (I'JU), Xo. 1, p. G; 

 abs. in Dot. Ccntbl., 119 (1912), No. 21, p. 525). — This fungus, when grown in 

 pure culture upon Raulin's solution, produces a new organic acid termed 

 penicillic acid and thought to belong to the general class called lichen acids. 

 It is stated to be moderately toxic, antiseptic in its action, and a protoplasmic 

 poison. Since lichens ax'e symbiotic forms, composed of fungi and algai, the 

 finding of this type of substances in the pure culture of a fungus makes it seem 

 probable that in lichens, the lichen acids are the products of the fungus metab- 

 olism, and not of that of the algte. 



Some conditions influencing nitrogen fixation by aerobic organisms, W. B. 

 BoTTOMLiiY {Proc. Roij. Soc. [London], Ser B, So {1012), Xo. B 5SJ. pp. 

 it6-468). — A study has been made of Azotobacter and Pseudomonas separately 

 atd in combination to determine a suitable form of sugar for the growth of 

 these nitrogen-fixing organisms. 



Under usual conditions mannite is found most efficient for the growth of 

 Azotobacter and maltose for Pseudomonas. The author's investigations, how- 

 ever, show that dextrin is about as efficient as maltose for Pseudomonas and 

 as mannite for Azotobacter, while for a mixed culture of the two organisms 

 it is much more efficient than a mixture of maltose and mannite. For both of 

 these organisms the author recommends a simple and effective nutrient medium 

 obtained by adding to distilled water 1 per cent dextrin, 0.2 per cent dipotas- 

 sium phosphate, 0.02 per cent magnesium sulphate, and 0.4 per cent basic slag. 



The influence of temperature on the movement of zoospores of Chlamydo- 

 monas, P. Dkskociie {Compt. Rend. Acad. Sci. [Paris], 15^ {1912), A'o. 19, pp. 

 nU-i2J,7, fi(j. 1; Compt. Rend. Soc. Biol. [Paris], 72 (1912), Nos. 17, pp. 7.',8- 

 750; 18, pp. 793-795, fig. 1). — Continuing previous studies on Chlamydonionas 

 (E. S. R., 26, p. 431), the author found that the range of temperature within 

 which movement of the zoospores is possible extends from the freezing point 

 on the one hand to about 40° on the other, provided the containing water be 

 Aery slowly warmed. Nearly all, however, became inactive between 30 and 

 32°. This fact and the facts of individual differences of endurance at given 

 temperatures, of behavior on slower or more rapid warming, and of recovery 

 on cooling make it difficult to fix a maximum limit of temperature for the 

 activity of Chlamydonionas. 



If the water containing the zoospores be very slowly warmed to 39° and 

 there maintained, in about 15 minutes a marked degeneration of the cilia is 

 observable which results in their complete disappearance in about 1 hour. The 

 author remarks that the degeneration of cilia in this case is quite comparable 

 with that observed in the case of Pythium and Saprolegnia, very different 

 organisms from the one here studied. 



Studies in seeds and fruits, H. B. Guppy (London, 1912, pp. XII+528, figs. 

 6). — This book is the result of a study begun on the rest period of seeds and 

 includes observations on some of the factors which are concerned in the rest 

 period and germination of seeds, the relation of seeds to fruits, etc. Among 

 the factors discussed are permeability, h^roscopicity, role of shrinking and 

 swelling of seeds, homologies of fruits, dehiscence of fruits, relation of number 

 of seed to weight and size of the fruit, abortion of ovules, seed coloration, and 

 rest period of seeds. 



The influence of organic acids and glucose on the respiration of seeds 

 during their swelling, Mile. G. Peomsy (Rev. Gen. Bot., 24 (1912), No. 283, pp. 

 S13-318).— In a previous paper (E. S. R., 25, p. 222) the author showed the 



