406 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and on the tliickness of the pit-closing membrane ; and in many 

 cases the only evidence of such perforating threads is afforded by the 

 general staining of the membrane. Every transition occurs between 

 clearly defined threads in the substance of the closing membrane, and 

 the mere staining of that structure as a whole. 



The author has found in all pitted tissues a pit-closing mem- 

 brane which is made evident by staining thin sections with iodine 

 and mounting in chlor-zinc-iod, and has never seen open pits. The 

 continuity of the protoplasm is always established by means of fine 

 threads arranged in a sieve-structure, and not by means of compa- 

 ratively large processes which the occurrence of open pits would 

 necessitate. 



A continuity of the protoplasm between adjacent cells occurs in 

 Dioncea muscipula, and is especially pronounced in the most central 

 layers of parenchymatous cells. The parenchyma-cells of the petioles 

 of certain plants, which are often thick- walled and conspicuously 

 pitted, afford favourable material for investigation. In Aucuba japonica 

 and Prunus lauro-cerasus distinct threads can be made out crossing the 

 pit-closing membrane. In Ilex Aquifolium there is a doubtful stria tion, 

 and in others examined a mere coloration of the pit-membrane. 



The author believes the connection of cells with one another to be 

 a universal phenomenon, and the functions of the filaments to be as 

 follows : — In sieve-tubes and in endosperm-cells they make possible 

 a transference of solid materials ; but in ordinary cells their only pur- 

 pose is to establish a communication of impulses from one part of 

 the plant to another. 



By means of the methods described Mr. Gardiner has examined 

 the seeds of about 50 species of palms, as well as those of repre- 

 sentatives of the orders Leguminosse, Eubiaceae, Myrsinese, Loga- 

 niaceae, Hydrophyllace^, Iridaceae, Amaryllidacese, Dioscorese, Melan- 

 thaceae, Liliacese, Smilaceae, and Phytelephasiese, in all of which he 

 found that the cells of the endosperm are placed in communication 

 with one another by means of delicate threads traversing their walls. 



Living and Dead Protoplasm.* — 0. Loew makes a final defence 

 of his views as to the essential difference between living and dead 

 protoplasm, and the aldehydic nature of the former. The facts relied 

 on are mainly the following : — (1) the rise of temperature on the death 

 of the cell ; (2) the sudden setting in of an acid reaction ; (3) the 

 fact that living protoplasm does not precipitate any pigment, while 

 dead protoplasm does. The author states that the substance described 

 by Eeinke under the name of plastin, is an impure albuminoid soluble 

 with difficulty in dilute potassa; and that nuclein is also chiefly 

 composed of an albuminoid combined with phosphoric acid. 



Occurrence of Protoplasm in Intercellular Spaces.f — Gr. Berthold 

 notices several instances of the occurrence of this phenomenon : — in 



* Bot. Ztg., xlii. (1884) pp. 113-20, 129-32. Of. this Journal, i. (1881) 

 p. 906 ; ii. (1882) pp. 67, 361, 440, 522 ; iii. (1883) p. 225. 

 t Ber. Deutsch. Bot, GeselL, ii. (1884) p. 20. 



