78 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Independently of the layers, probably functionless, wbicli lie above 

 the cork, the number of zones of active bast is only small. The 

 increase amounts at most to 1/5, usually to not more than from 

 1/10 to 1/20 of the total increase of the wood. 



In order to distinguish between hard and soft bast the author 

 employs anilin sulphate, which stains yellow the elements of the 

 hard bast only. The hard bast appears to be formed first out of the 

 cambium. On each ring of wood, two zones of bast are often formed 

 annually, but one only, or more than two, are not uncommon. In 

 the older stems of many plants the formation of groups of scleren- 

 chymatous cells in addition to bast-fibres is frequent. 



Lenticels and the mode of their replacement in some woody 

 tissues.* — H. Klebahn adopts Stahl's classification of the lenticels of 

 dicotyledons and conifers under two types, viz : — (1) those composed 

 of loose cork- cells with denser intermediate strisB, and (2) those with 

 closely packed cork-cells without intermediate striae. The former 

 kind occur in Sophora, Rohinia, Alnus, Betula, Crataegus, Sorbus, 

 Prunus, and ^sculus ; the latter in GingJco (Salishuria), Sambucus, 

 Lonicera, Euonymus, Cornus, Salix, Myrica, and Ampelojpsis. In both 

 cases he regards the function of the lenticels to be as organs of 

 aeration, to promote both the interchange of gases and transpiration. 



The author then investigates by what means this function is per- 

 formed in those climbing shrubs which are destitute of lenticels, and 

 finds, in all cases, in the medullary rays, a number of parallel inter- 

 cellular spaces running in a radial direction through the wood, cam- 

 bium, and cortex. They are in communication with the intercellular 

 spaces of the wood on the one hand and of the primary cortex on the 

 other hand, and form a very efficient system of aeration for the wood. 



Gum-cells of Cereals.! — Johannsen objects to the term " gum- 

 cells " (Kleherzellen), applied by Hartig to certain cells in the grains 

 of cereals. On examining thin sections which had been preserved for 

 years in alcohol, he found in these cells a very evident protoplasmic 

 network or system of chambers, the contents of which, probably 

 drops of oil, were soluble in alcohol. Sections of dry grains of wheat, 

 rye, and barley examined in water show in these cells numerous 

 round strongly refringent bodies of nearly uniform size, and larger 

 drops, clearly of oil. Both are stained brown by osmic acid, but only 

 slowly yellow by iodine-water. They consist of oil. 



Separate portions of the protoplasmic network were also examined, 

 the meshes of which were nearly as large as the smallest drops of oil. 

 Sometimes they are also stained by osmic acid, and therefore con- 

 tain oil. The sections were heated for a day or longer with absolute 

 alcohol containing 2 per cent, of corrosive sublimate, when nothing 

 but a protoplasmic network was always left behind, coloured by iodine 

 or anilin-blue. 



Since even the most soluble proteinaceous substances become 



* Ber. Deutsch. Bot. Gesell., i. (1883) pp. 113-21 (1 pi.), 

 t Mecldel. Bot. Foren. Kjobenhavn, 1883. See Bot. Centralbl., xv. (1883) 

 p. 305. 



