CH. V] LAMINARIA. 113 



(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. It will be found to have increased far 

 more in the transverse than in the longitudinal direction. 



(129) Effect of temperature^. 



Weigh, to O'l 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 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 from two to two and a-half times as much 

 water as the second lot-. 



(130) Salt solution. 



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 



^ See Reinke in Hanstein's Botan. Abhand. iv. 



- According to Nobbe {Handbuch der Samenkunde, 1876, p. 230) the 

 effect of temperature is not very apparent when peas are soaked for longer 

 periods. 



D. A. 8 



