SECTIONAL TRANSACTIONS.— K. 403 



These facts support current tlieories on the sequence of changes in cell respiration, 

 and the recentl.y won knowledge of the enzymes and of the cytochrome exchange 

 system at work during respiration. 



When results obtained by a single experimental method fail by themselves to 

 convince, as is the case in most problems of metabolism, the multiplication of methods 

 becomes an urgent need. Although interference with the usual production — removal 

 sequences, by varj'ing the external environmental conditions — is not a new mode of 

 investigation, its scope has been considerably extended in recent j'ears. Its use in 

 work on sugar respiration in plants points to the importance of acetaldehyde as a link 

 in the chain. 



Many of the experiments have been carried out on apples, and some of them have 

 already clarified ideas on certain physiological diseases of storage of apples and pears. 



Prof. D. Thoday and Mr. N. Woodhead. — The Growth and Metabolism of 

 Kleinia articulata. 



In the sunflower stem the increase in vascular tissue, and especially of xylem, is 

 organised sectorially in correlation with the development of the leaves with which 

 it is in direct communication, and from an early stage the parenchymatous tissues 

 accommodate themselves to the unequal growth of the different parts, and later 

 are variously stretched (Thoday, Annalsof Botany, 36, 1922, 489-510). This relative 

 passivity of the parenchyma, in contrast to the ordinary conception of the part it 

 plays in growth expansion, led to a study of a succulent composite, Kleinia articulalii. 

 Here the bundles are all small and widely separated. Only in stems bearing branches 

 is interfascicular cambium developed, and even then vascular tissue is only 

 differentiated in a few very small groups. Growth in diameter occurs in two stages, 

 an early stage dviring the first expansion of the stem, and towards the end of the 

 orowing period ; in the latter the pith becomes fissured. Nitrogen starvation 

 favours swelling at both these stages. Shading results in ver}>- slender stems, the 

 structure of which suggests interpretation as young unswoUen stems ; and the slender 

 inflorescence axis is very similar. In the rhizome, on the other hand, secondary 

 growth is pronounced and a periderm is formed — in the slenderest a continuous 

 zone of woody tissue is formed, in the thicker the zone is discontinuous. 



A continuous zone of wood is also found at the narrow constriction between an 

 aerial branch and its parent stem ; here all the tissues are liquefied except the local 

 periderm and small phloem groups. 



Nitrogen starvation in sand culture resulted in abundant rhizome formation, but 

 did not affect the time of flowering. 



Mr. H. Evans. — Buffemig and Acidity in Kleinia articulata. 



The titratable acid-content is low as compared with the values given by Hempel 

 for Kleinia cuneifolia, but of the same order as in certain other succulents with a 

 relatively low acid-content. 



Preliminary observations on the effect of light and darkness showed that the 

 plants were rather variable in their reaction, the acidity often diminishing in darkness. 



The stem is almost invariably richer in acid than the leaves, and generally the 

 acidity increases from the tip to the base of a stem. The outer tissues are invariably 

 richer in acid than the pith. 



The difficulty in obtaining a well-defined end-point in the titration of the extracts 

 with alkali led to some observations on the buffer system. The original intention was to 

 gain more information about the best conditions for titration by construction of titra- 

 tion-curves. The pH values were obtained by the use of Gillespie's drop-ratio method. 

 It was found that there was an extensive buffer system at the region of pH correspond- 

 ing to the end-point. Analysis of the sap showed that the acid present was malic 

 acid, and extracts, especially of old stems, gave a well-defined inorganic phosphate 

 reaction. A precipitate is formed on titration of the juice with alkali, and this was 

 found to be partly composed of calcium phosphate. Titration-curves of mixtures of 

 calcium phosphate and malic acid were very similar to the titration-curves of the extract 

 of old stems. Young stems showed a different type of curve, approximating more 

 closely to the titration-curves of mixtures of aluminium malate and malic acid. 

 Calcium phosphate plays an increasingly important part in the buffer system, with 

 increasing age of the stem from which the extract is made, since both calcium and 

 phosphate accumulate with age. 



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