104 PLANT PHYSIOLOGY 



H- 35. 36, 37- f or mm g- 



11. 53-5, for No generalizations . . . of respiration, read In such a desiccated 



condition respiration is doubtless so restricted that one is entitled to regard it 

 as without any physiological significance. From these, as well as from certain 

 recent researches of P. BECQUEREL (1906), we must conclude that respiration 

 is not necessary to the maintenance of the capacity for germination, and that 

 during the resting period it may exist in a condition of absolute physiological 

 inactivity, comparable to a wound-up but motionless clock. Whether this is 

 true of all desiccated seeds, we do not know. 



342, 11. 19-27, for It is now . . . external conditions, read It is well known 

 that these differences are in part due to the variable permeability of the testa 

 to water, so that in the single individual the \vater required for development 

 reaches the embryo at different times. On the other hand, however, seeds 

 are known which, in spite of their permeability to water, germinate only after 

 a certain rest period. This is the case, according to WINKLER (1898), in Viscum, 

 and w y e must leave it undecided at present whether in this case internal change 

 or removal of external inhibitives (poison from the fruit mucilage) is the effec- 

 tive agent. According to FISCHER (1907) the seeds of many aquatics do not 

 germinate in spite of the presence of water ; in their case, apparently, chemical 

 stimuli from without initiate germination. 



343, 11. 35-6, for This must be ... of the old. read We cannot conclude from 

 this that the phenomena of periodicity in longitudinal growth is to be attributed 

 to periodic changes in external conditions and their after-effect. 



1.55 P. 345, 1. 35, for The winter buds . . . worthy of notice, read Doubt- 

 less, there are trees and shrubs which go on unfolding leaves continuously 

 under favourable external conditions. We should expect behaviour of this 

 kind more especially in the tropics, where moisture and temperature show no 

 variations worth mentioning. In Buitenzorg VOLKENS (1903) observed con- 

 tinuous leaf-formation in Albizzia moluccana and Filicium decipiens ; probably 

 Ficus elastica behaves in the same way (BERTHOLD, 1904), yet this plant under 

 favourable conditions, as e.g. when grown in a room in this country, passes 

 through a winter rest period. Apparently, we have to deal with the same 

 phenomenon in roses, and many other shrubs ; they go on forming leaves in 

 autumn if placed in a hothouse, but in the open their growth comes to a stop for 

 other reasons. In all plants of this kind, as the shoot becomes higher and 

 higher, the supply of water and nutrient salts to the apex, and of organic 

 materials to the roots, becomes continually more difficult, and their growth, 

 for internal causes of this nature, cannot be unlimited. It may be assumed, 

 however, that the growing point might be maintained in a growing state for 

 hundreds of years, if it could be arranged that new roots should be formed 

 on the stem at a certain distance from the apex, and that these should be 

 preserved under favourable vital conditions. 



In the tropics, however, the majority of trees behave quite otherwise ; 

 during leaf formation, times of vigorous activity alternate with periods of out- 

 ward rest. Often in a few days buds become transformed into elongated twigs 

 on which new buds are formed, and which, later on, unfold suddenly. An 

 illustration of this phenomenon is seen in Hevea brasiliensis. In the ever warm 

 and moist climate of the Brazilian rain forest near Para the main axis shoots 

 intermittently a large number of times during the year. In one case, HUBER 

 (1898) noticed the commencement of new shoots on Dec. 10, 1896, Jan. 20, 

 Mar. 12, April 25, June 6, 1897, each of which required about thirty days to unfold 

 its leaves, followed by a quiescent period of about ten days. Besides these 

 five shoots the plant formed three more during 1897. Each shoot began with 



