Red Wood 111 Colli f(')'s. 



109 



screw micrometer eyepiece, in both the red and white wood. 

 Sections were cut of the main stems of several of the plants, 

 Avhich had been growing in the pot^ placed on their sides from 

 20th September to 28th November, 1906. 



Taking the averages of the thickness of the walls in the red 

 and white wood, the two sets of readings being taken from the 

 same section as nearly diametrically opposite as possible, in 

 practically eveiy case, the walls of the white tracheides were 

 found to be thicker than those of the red, whilst the cavities 

 of the traeheides of the white wood were smaller in diameter 

 than those of the red tracheides. 



These results are not in accordance with those previously 

 recorded by Son n tag, ^ who found that the walls of the 

 tracheides in the red wood were thicker than those of the white. 



Experimental Results. 



A number of readings were taken of the internal diauietors 

 and the thickness of the walls of the tracheides, and the results 

 are given in the form of averages of sets of tive readings, fol- 

 lowed l)y a\erages of tliese again. 



Taxus baccata. 



In the thickest part of the i-ed wood in the sections exannned, 

 the tracheides were 20 deep. 



Section I. 



Red Wood White Wood 



Internal Diameter Thickness of Wall Internal Diameter Thickness of Wall 



.008 mm. .004 mm. .008 mm. .008 mm. 



.009 •, .004 ., .008 ,, .008 ., 



.011 ,, .004 ,, .008 ,, .007 ,, 



.012 .. .005 ., .009 ., .007 ,, 



Average 

 .010 mm. 



Average 

 004 mm. 



Average 



.008 mm. 



Average 

 .008 mm. 



1 Jahrl). fur vviss, Bot., Bd. xxxix., p. 71. 



