442 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Tho inequalities in the radial diameter of older bast-cells in Ascle- 

 piadese and Apocynaceai does not result from constriction or compression 

 of tlio narrower, but from a later widening of the broader part, which is 

 always accompanied by a new formation of lamellae of cellulose, com- 

 mencing usually with the formation of fine transverse lanielloa and caps. 

 Remains of protoplasm could often be detected between the separato 

 cap-like pieces. A very distinct formation of caps takes place also at 

 the ends of the bast-cells of Euphorbia palustris. 



The local widenings of bast-cells can bo explained only on the sup- 

 position of a superficial growth depending on intussusception. This 

 the author claims to have proved by measurements, which show that 

 the superficial increase could not be the result of simple stretching of the 

 cell-wall. 



The spiral striation of bast-cells the author believes to be always the 

 result of subsequent differentiation in an at first homogeneous cell-wall, 

 which advances in a centripetal direction. Besides this spiral striation, 

 he observed in bast-cells a transverse stratification resulting from actual 

 differentiation of the substance of the cell-wall. This differentiation 

 also arises at a late period, but is said again to disappear in older 

 bast-cells. 



As a general result, the author concludes that, in addition to growth 

 by apposition and by intussusception, there is also a periodic fresh 

 formation of cell-wall, proceeding exclusively from the protoplasm, and 

 independent of the portions of cell- wall already in existence. This new 

 formation is not always accompanied by a contraction of the protoplasm, 

 as is shown by the inclusion of masses of protoplasm in the formation 

 of caps. But the caps do not always show the same chemical reactions, 

 and it is probable that at later stages they are sometimes permeated by 

 albuminoids. 



Growth of the Cell-wall.* — From the experimental application of 

 staining reagents, Dr. F. Noll has come to the conclusion that the mode 

 of growth of the cell-wall is chiefly by apposition, while of the part 

 played by intussusception there is no definite proof. The experiments 

 were made chiefly on unicellular Siphoneae, species of Bryopsis and 

 Derbesia, by causing the production of Berlin blue in the cell-walls of 

 the growing plant by the use of potassium ferrocyanide and iron chloride. 

 The apical growth, however, takes place by a kind of " eruption " ; the 

 old membrane bursts, and the membrane of the young shoot is formed 

 entirely of new material. The growth of the "leaves" of Caulerpa 

 takes place especially in this way. From the fact that no surface- 

 growth of the cell-wall has been observed independent of turgidity, the 

 author concludes that a growth by apposition may be hereafter experi- 

 mentally proved in the case of the cells of the higher plants similar to 

 that which he has demonstrated in some Siphoneae. 



Morphology and Physiology of the Cell.f — As a section of the 

 third volume of Schenk's ' Handbuch der Botanik,' Herr A. Zimmermann 

 publishes an exhaustive treatise on this subject. After a general in- 

 troduction he treats of the following subjects : — The form of the proto- 

 plasmic body, the finer structure and chemical composition of the 



* Abhaudl. Senckenberg. Naturf. Gesell., xv. (1887) pp. 101-62 (1 pi.). 

 + ZimmemiauD, A., ' Die Morphol. u. Physiol, der Plitiuzenzelle,' 223 pp. and 

 36 figs., Breslau, 1887. 



