102 LAMINARIA. [CH. V 



(128) Increase of size not uniform in direction. 



Cut a rectangular piece out of the thallus of Laminaria, 

 choosing a part free from wrinkles; let it be slightly- 

 oblong so that the longitudinal axis of the thallus may be 

 distinguishable. Measure the length and breadth with a 

 millimeter scale and mark, by means of a pin hole in the 

 corner, the two edges along which the measurements were 

 taken. Place it in water and measure it again in a 

 quarter of an hour, and again in an hour. It will be 

 found to have increased far more in the transverse than 

 in the longitudinal direction. 



(129) Effect of temperature. 



Weigh, to 0*1 gram, about 30 grams of air-dried peas : 

 place them in water at about 26° C, and let them remain 

 at that temperature for 2 or 3 hours. Dry them first with 

 a soft cloth, then with filter paper, and weigh them again. 

 Place at the same time a similar weight of peas in water 

 at 10° — 14° C. and compare the gain in weight in the two 

 cases. The peas, which have been in warm water, will 

 have absorbed much more water than the second lot. 



(130) Salt sohition. 



Weigh about 30 grams of peas, taking care to use the 

 same material as that employed in experiment 129 ; place 

 them in 10 per cent. NaCl solution, which must be kept 

 at the same temperature as the cool water in experiment 

 129. After 2 or 3 hours (as the case may be) dry and 

 weigh them. The peas will be found to have increased in 

 weight, but much less than the control material in 

 experiment 129. 



