AGEICULTUKAL BOTANY. 329 



thus, and other plants the foliage of which is characterized at times by a deep 

 red coloration. 



The author claims that the appearance of anthocyanin is correlated with an 

 accumulation of oxygen in the tissues and its disappearance with a noticeable 

 loss of that gas. The variation in the gas exchange is regulated by the chloro- 

 phyll activity; hence the formation of the red coloring matter is intimately 

 connected with assimilation. The actual formation of the red pigment Is due 

 to the accumulation of carbohydrates in the cells, and perhaps the glucosids 

 undergo a kind of oxidation by which they are transformed into anthocyanin. 



The role of catalase in plants, Anna Rosenberg {Ber. Dent. Bot. GeselL, 28 

 (1910). No. 7, pp. 280-2SS). — A study was made of the catalase activity of 

 various seeds, the seed being digested with water, allowed to stand for an hour, 

 mixed with Merck's Perhydrol (hydrogen peroxid), and the oxygen given off 

 determined by a manometer. A number of experiments were carried out with 

 seeds representing cereals, leguminous plants, and oil-bearing plants, and also 

 with wheat seedlings, which showed that the catalase acted as an aerobic 

 ferment. 



The chemistry of chlorophyll, R. Willstattee (Rpt. Brit. Assoc. Adi\ Sci., 

 1909, pp. 667, 668). — An abstract is given of a paper read by the author before 

 the British Association in which he gives a summary of the present state of 

 information relative to the chemistry of chlorophyll. 



He claims that the older investigations showed little regarding the nature 

 of chlorophyll, but that the recent discovery that phylloporphyrin, a degra- 

 dation product, is closely related to derivatives of hjemin, is very important. 

 The difference between chlorophyll and haemin in regard to the metal held in 

 their molecules is of vital importance. The author has established that the 

 chlorophyll of all classes of plants contains magnesium and no other metal, 

 and that the magnesium in the chlorophyll has an important part in the assimi- 

 lation of carbon dioxid. He claims that failure to detect the presence of 

 magnesium in chlorophyll is probably due to the fact that chlorophyll is very 

 sensitive toward acids, which completely eliminate the metal. 



In investigating the action of alkali on chlorophyll it was found that the 

 continued action yields first green chlorophyllins, then blue glaucophyllin and 

 red rhodopliyllin, and finally red pyrrophyllin and phyllophyllin. 



Gentle warming with acids has led to the discovery of phytol. This appeared 

 to be present in nearly all plants examined, although it is not believed to be 

 an essential component of chlorophyll. Out of more than 100 species of plants 

 examined, only in a few species of Labiatte and Solanacese was there any ex- 

 ception to the occurrence of phytol in the chlorophyll. 



Perception of light in plants, H. Wager {RjH. Brit, Assoc. Adv. Sci., 1909, 

 p. 67 Jf). — Attention has been previously called (E. S. R., 22, p. 26) to the sug- 

 gestion of Haberlandt that light perception on the part of plants is a function 

 of the cytoplasm lining the epidermal cell walls. The author thinks that on 

 morphological and physiological grounds this is not a satisfactory explanation, 

 and proposes the alternative view that the chlorophyll grains are the percipient 

 organs. He claims that the rays of light which are absorbed by the chlorophyll 

 are the only ones which appear to be functional in heliotropism, and that these 

 by their action on the various coloring materials contained in the chlorophyll 

 may set up in the cytoplasm changes necessary to bring about the stimulus. 



The effect of longitudinal compression upon the production of mechanical 

 tissue in stems, L. H. Pennington (Bot. Gaz., 50 {1910), No. J,, pp. 257-28Jf, 

 flgs. 2). — An investigation was luidertaken with woody and herbaceous plants 

 to determine experimentally the effect of weight which produced longitudinal 

 compression in vertical stems. The experiments with woody plants were con- 



