156 PHYSIOLOGY [BoT. Absts., Vol. IX, 



largely overcome by salts yielding the Ca"*""*" ion, to a much less degree by those yielding the 

 Mg"^"*" ion, and very slightly or not at all by those yielding theK+orNa+ions. The calcium 

 salts absorbed most abundantly are CaCl2, CaCOs, and Ca(N03)2. Absorption of electro- 

 lytes is increased by an increase in the number of kinds of nutrient ions present in the solution. 

 When accompanied by Ca"*"*" ions, the K+ ions — neglected when offered in simple solutions — 

 are absorbed. As the variety of ions present in the solution is increased, the importance of 

 rather sharply marked proportional relations becomes distinctly less than in the simpler 

 solutions. The most striking single chemical condition of the solution is the presence of a 

 certain minimal quantity of Ca"^"*" ions. A certain minimal quantity of Ca"^"^ ions seems to 

 be necessary to secure the normal absorption of the other required ions present in the soil 

 solution. Ca ions evidently make "physiologically available" the other nutrient materials 

 contained in the soil solution. The basis, then, for an understanding of special service per- 

 formed by the Ca"^~^ ion is doubtless to be sought in the physiology of the cell. — F. M. Sckertz. 



PHOTOSYNTHESIS 



1003. Stern, Kurt. Untersuchungen iiber Fluorescenz und Zustand des Chlorophylls 

 in lebenden Zellen. [The fluorescence of chlorophyll, and its condition in living cells.] Ber. 

 Deutsch. Bot. Ges. 38: 28-35. 1920. — By means of the spectroscope the author has studied 

 the fluorescence of living cells of Chlorella suspended in water and of solutions of chlorophyll 

 in various lipoids. Since fluorescence was observed in the suspension of living cells and n the 

 solutions in lipoids, but never in the colloidal solutions in water, even when various substances 

 were added which might be conceived of as rendering chlorophyll in colloidal solution in the 

 chloroplast fluorescent, he concludes that in the intact green cell the chlorophyll is in true 

 solution in a lipoid. He states further that the process of assimilation of carbon dioxide 

 goes on partly in a lipoid, partly in a hydroid phase. Surface active substances alter the 

 bounding surfaces of both phases and thus hinder or stop assimilation. — R. M. Holman. 



1004. Weber, Friedl. Notiz zur Kohlensaureassimilation von Neottia. [Carbonic 

 acid assunilation by Neottia.] Ber. Deutsch. Bot. Ges. 38: 233-242. 1920.— The author 

 reviews the literature relating to the ability of the brown, also chlorophyll-containing, chro- 

 matophores in the cells of the inflorescence of the saprophytic orchid, N eottianidus avis, to 

 assimilate carbon dioxide. Interest in the question has been renewed since Wilschke's 

 discovery that the green pigment in question contains only a-chlorophyll and none of the 

 6-component of ordinary chlorophyll. The negative results of Willstatter and Stoll 

 are not considered conclusive by the author of the present paper. — The author found that the 

 starch, which has long been known to be present in the cells of the brown inflorescence, does 

 not disappear when the shoots are kept in the dark for many days; and that plants which 

 have not been exposed to light at any time during their development, aH ough strikingly 

 etiolated and without either chlorophyll or the characteristic brown coloration, are never- 

 theless rich in starch. Neottia chromatophores are without that ability to reduce silver salts 

 in darkness which Molisch found in the chloroplasts of all the phanerogams which he in- 

 vestigated, though weak in the case of green orchids and absent in certain diatoms and in 

 Hydrurus. These 2 last mentioned groups, according to Wilschke, lack the chlorophyll 

 component h. The author's attempts to determine by Engelmann's bacterial method whether 

 oxygen was liberated by illuminated tissue containing chromatophores were not successful. 

 Positive results were secured by the use of reduced indigo carmine solution, but the author 

 believes the question not yet conclusively answered. — R. M. Holman. 



1005. Willstatter, Richard, und Arthur Stoll. Untersuchungen iiber die Assimila- 

 tion der Kohlensaure. [Investigations of the assimilation of carbon dioxide.] 448 -p. Julius 

 Springer: Berlin, 1918. — A collection of seven papers: I. The constant chlorophyll-content 

 during photosynthesis. The chlorophyll content of leaves is 0.15 - 0.35 gm. per 100 gm. fresh 

 weight; 0.6 - 1.2 gm. per 100 gm. dry weight, and 0.3 - 0.7 gm. per sq. m. leaf surface. The 

 carotinoids are 0.07 - 0.20 per cent of the dry weight, or 0.03 - 0.07 gm. per sq. m. Normal 

 plants show a constant relation between the chlorophyll components a and b, designated 



