90 SUMMARY OF CUERENT RESEARCHES RELATING TO 



plasm, in which the resultant of the chemical and physical forces pro- 

 duces a state which we call life, offers a remarkable resistance to all the 

 actions which would interfere with the harmony of these forces. The 

 degree of this resistance varies with the individual, but the end is always 

 the maintenance of the integrity of the organism. This result is more 

 easily obtained when the organism is of simple constitution ; and the 

 equilibrium which exists between the forces is more stable than when 

 the organism is more highly constituted and the equilibrium is more 

 easily disturbed. 



Action of Oxygen under high pressure on growth.* — From the 

 result of experiments on various flowering plants and on Phycomyces 

 nitens, Herr S. Jentys finds that an increase of the partial pressure of 

 oxygen up to one atmosphere does not, in most cases, exercise any per- 

 ceptible influence on the rapidity of growth. Only in a few cases is 

 there a distinct acceleration. Beyond one atmosphere an increase in 

 the pressure of oxygen retards growth in proportion to the increase. 

 The result is the same if the increased pressure is due to nitrogen. 

 The author believes compressed oxygen to have a directly injurious 

 effect upon the growth of the plant. 



Influence of the Substratum on the Growth of Plants.f — Herr S. 

 Dietz finds that the influence said to be exerted by the substratum on 

 the direction of the growth of the hypocotyledonary portion of plants 

 is due entirely to heliotropism, since it is not exercised in the dark. 

 Heliotropism and haptotropism both exercise an influence on the 

 sporangiophores of Phycomyces nitens; the contact of fine wires and 

 tinfoil affects the direction of growth even at an early stage before the 

 complete formation of the sporanges. 



Conduction of Fluids through the Alburnum. | — From observations 

 made mainly on the birch, Herr E. Hartig confirms his previous con- 

 clusions that the younger or outer alburnum of a trunk is the part 

 through which the conduction of water chiefly takes place, the inner 

 alburnum and duramen taking but a subordinate part in it. He takes 

 the opportunity also of expressing his general concurrence with the 

 conclusions of Wieler.§ 



(3) Irritability. 



Porces which determine the Movements in the Lower Organisms. [| — 

 Dr. E. Aderhold has attempted to ascertain the causes which determine 

 the movements of swarm-spores and of some of the lower algae. In the 

 first place with regard to rheotropism and aerotropism, he is of opinion 

 that the former does not exist, while Euglena is certainly positively 

 aerotropic. The geotropic sensitiveness of Euglena can be demonstrated 

 when the aerotropic movement is prevented. Similar phenomena to 

 those of Euglena are presented also by the mega- and microzoospores of 

 Ghlamydomonas pulvisculus, by JSsematococcus lacustris, and by the swarm- 



* Unters. Bot. Inst. Tiibingen, ii. (1888) pp. 419-64. Sec Bot. Centralbl., xxxvi. 

 (1888) p. 105. 



t Unters. Bot. lust. Tubingen, ii. (1888) pp. 478-88. See Bot. Centralbl., xxxvi. 

 (1888) p. 106. X Ber. Deutsch. Bot. Gesell,, vi. (1888) pp. 222-5. 



§ See this Journul, 1888, p. 768. 



II Jenaisch. Zeitsch. f. Naturw., xxii. (1888) pp. 310-42. See Bot. Ztg., xlvi. 

 (1888) p. 621. 



