PHYSIOLOGY 



255 



would penetrate into the cell membrane, as particles of colouring matter may be 

 introduced with the imbibition water into a colloid organic substance C 86 ). 



The process of elongation has so far been considered only in 

 relation to the single cell, preparatory to the consideration of the 

 phenomena presented by the growth of multicellular organs. With 

 regard to this it is to be noted that the intensity of growth in two 

 organs of equal total growth is greater the shorter the growing zone 

 is. BUCHNER observed in fungal hyphae and pollen tubes in which 

 growth is restricted to just behind the apex that its amount per unit 

 of time was 220 per cent as compared with i-1 per cent in the 

 majority of the higher plants. 



The operations of growth in plant organs proceed very slowly ; so 



Fit;. 21(5. .Simple and .self-reyisterinj; auxanometer. For description see text. 



slowly as to be, in general, imperceptible. Only some fungal hyphae 

 and the stamens of many Gramineae grow so rapidly that their elonga- 

 tion is evident, even to the naked eye. The hyphae of Dictyophora 

 grow in length to the extent of 5 mm. per minute (A. MOLLER) and 

 according to ASKENASY, an increase in length of 1'8 mm. a minute 

 has been observed in the stamens of Triticum (Wheat). This approxi- 

 mately corresponds to the rate of movement of the minute-hand of a 

 watch. In comparison with these, the next known most rapidly 

 growing organ is the leaf-sheath of the Banana, which shows an elonga- 

 tion of I'l mm., and a Bamboo shoot, an increase in length of 

 0'6 mm. per minute; a strong shoot of Cucurbita grows O'09-O'l mm. 

 per minute, while most other plants, even under favourable circum- 

 stances, attain but a small rate of elongation (O'OOS mm. and less 

 per minute) ( 67 ). 



