490 SUMMARY OF CURUENT RESEARCHES RELATING TO 



Movement of Water in Plants.* — M. E. (Jodlowski accounts for 

 all the iilR-noniona of '' blecdiiig-jiressurc " by the following cx])lana- 

 tions: — (1) Tliat in the cells where this pressure originates, i)erio(li- 

 cally recurring splittings ami chemical re-formations succeed one 

 another within certain periods; (2) That at the time when the water 

 is expelled from the cell by turgidity in consequence of the diminution 

 of the osmotic attraction of the cell-sap, the protoplasm offers the 

 least resistance to filtration at the spot where the cell is in contact 

 with a fibro-vascular element. 



Importance of Dead Tubes and Living Cells for the Conduction 

 of Water' in Plants.t — Ilerr M. Westermaier brings forward prac- 

 tical and theoretical considerations in favour of the following points 

 in the movements of water in plants, viz.: — (1) The anatomical fact 

 of the intimate contact between the jiarenchymatous and the vascular 

 systems has for its chief purpose the combined action of both systems 

 in facilitating the passage of water through the tissues, rather than 

 the isolated activity of either system ; (2) Living parenchyma by 

 itself can only bring about the passage of water from cell to cell 

 by suction through small spaces. 



Supply of Air to the Roots and Root-pressure. t — Dr. A. Hanson 



shows that an abundant supply of air to the roots is of advantage to 

 plants in two ways ; firstly in preventing by oxidation the formation 

 of sxilphide of iron, and secondly by preventing the accumulation of 

 alga) about the roots. Dr. Hansen also confirms the statement of 

 Sachs that root-pressure is not a necessary factor in the circulation 

 of fluids through the plant; but that even when the roots are killed, 

 they can absorb from the soil a sufficient amount of water to carry on 

 the process of transpiration and prevent withering ; they may even 

 under these circumstances expand their flowers. 



Nutations of Seedlings. § — Herr F. Kimmcr has experimented, 

 chiefly in the case of Phaseohis mnltijlorus, on the cause of tho 

 phenomena of nutation, whether the simple nutation of the hypocoty- 

 ledonary or of the cpicotyledonary portion of the axis, or the undu- 

 lating nutation resulting from the more rapid growth of one side of 

 the organ in its lower, of the other side in its upper part. The 

 following are the general results attained ; the investigation extend- 

 ing also to some other leguminous plants (]'/fm saiiva, Pimm sativum), 

 some monocotyledons {Cynosurus cristaius, Hordeum vidgare, &c.), and 

 some other dicotyledons [Hclianthus annuus, Cacurhita Pepo, &c.) : — 



1. The simple nutation of the hypocotyledonary segment in 

 Helicndhus, Cucurbita, and Phaseolus vuhjnris, is partly a spontaneous 

 phenomenon, partly dependent on gravity acting through the 

 cotyledons. 



2. The simple nutation of the cpicotyledonary segment is purely 

 spontaneous, and is connected with a certain amount of growth. 



* Pringsheim's Jahib. f. vhis. Bet., xv. (1884) pp. 569-630. 

 t SB. K. Prcuss. Akad. Wiss. Berlin, 1884, pp.^ 105-17 (1 pi). 

 X SB. riivs.-med. Oosell. Wiiizlnng, 1881, pp. 109-12. 

 § SB. K.k. Akad, Wiss, Wlen. Ixxxix. (1884) pp. 393-422. 



