AGRICULTURAL BOTANY. 29 



A new case of parthenocarpus development, R. Ewert (Jahreshcr. Ver. 

 Angcic. Bot., o ( liW7), pj). 8,3-85). — A report is given of tlie finding of a series of 

 apples lu 1907 that had developed without fertilization. The fruit was heavy 

 and of fine appearance, but was without a well-developed core, containing in 

 its stead a few ill-formed seed without any embryos. 



This led the author to a study of self-fertility among fruits and other plants. 

 He claims that self-fertility does not exist in strawberries, raspberries, toma- 

 toes, or currants. It occurs sparingly in the gooseberry and peach, somewhat 

 more frequently with the cherry and grape, and is most common among apples, 

 l)ears, and pumpkins. 



Some aspects of the mycorrhiza problem, C. B. Gruenberg (Bui. Torreij 

 Bot. Club, 3(! (lilOO), Xo. 3, iq). /6'J-/6'.'M .—Attention is called to some of the 

 phenomena associated with mycorrhiza, and the dependence of certain plants 

 on mycorrhiza is pointed out. The problem is one not only of great theoretical 

 interest, but may have important practical bearings upon the transplanting of 

 trees, reforestation, nitrification of soils, etc. 



The value of certain nutritive elements to the plant cell, H. S. Reed {Ann. 

 Bot. [London], 21 {1907), Ao. 8-'i, pp. 501-543, figs. 2). — The author describes 

 the results of a study upon the role of certain essential elements in the physi- 

 ology of the plant cell, particular attention being paid to the role of potassium, 

 phosphorus, calcium, and magnesium. The studies were made with filamentous 

 algje, the protonema of moss, prothalli of ferns, and root tips of phanerogamic 

 plants, these being selected on account of the possibility of submitting them to 

 microscopical examination in living condition. Nutrient solutions were prepared 

 and the role of the different chemicals studied. 



The algse were found to thrive best in artificial cultures which remained 

 neutral or slightly acid in reaction, while the phanerogams thrived best lu 

 neutral or slightly alkaline solutions. 



Potash salts were found necessary for the germination and growth of certain 

 mosses and for starch formation in all green plants studied. Mitotic cell 

 division never took place without a suitable supply of potassium. 



The lack of phosphorus seemed to be more injurious to the cells studied than 

 the lack of any other element. Cells suffering from phosphorus starvation lose 

 their soluble phosphorus, and later the injury extends to the living organs of 

 the cell, finally resulting in its death. Phosphorus appears to be more closely 

 connected with carbohydrate transformation than with its origin. In the 

 absence of phosphorus no mitotic divisions were jiossible. 



Calcium appears to be necessary for the activity and growth of the chlo- 

 rophyll and chlorophyll-containing organs. One of its most important functions 

 seems to be that of overcoming the bad effects of magnesium. Cell nuclei were 

 able to divide in the absence of calcium, but the new cell walls wei*e imperfectlj' 

 formed. 



Spore formation in Aspergillus was most abundant when magnesium and 

 phosphorus were present in the ratio of the normal culture solution used. An 

 excess of magnesium over phosphorus was detrimental to spore formation. 

 Magnesium .salts ai)pear to be necessary for the continued health and activity 

 of the chloroplasts. When grown in the absence of magnesium, there was no 

 oil formed in Vaucheria, and the processes of mitosis were somewhat retiirded 

 in the nuclei of Spirogyra. 



The nonliving parts of the cell, the cell wall, starch granules, oil globules, 

 etc., are the only ones visibly modified by the lack of an essential element. The 

 strictly living portions of the cell did not manifest any morphological changes 

 until they were killed. 



An extensive bibliography is appended to the article. 



