82 PLANT LIFE. 



The pressure at which it broke, 5,708 lbs., was much 

 more than was anticipated. The test was kindly 

 carried out for me by Professor Longbottom, to whose 

 kindness I am indebted for the use of his machine, 

 while I watched the fruit carefully and waited anxiously 

 for the result. Faint sounds of cracking were heard 

 even at 1,500 lbs., but these were simply the superficial 

 ridges yielding ; there was not the slightest distortion 

 until the enormous weight of 5,708 lbs. was employed 

 when the nut cracked with a report like that of a pistol 

 shot. 



Very often the food-stores of the Embryo are pro- 

 tected by bulbs or poisonous secretions. Most ordinary 

 drugs are obtained from Rhizomes, Seeds, Roots, etc., 

 which contain food material for the young plant. The 

 deadly poisons of Strophanthus and Nux vomica are 

 found in the seeds. The seeds of both are so peculiar 

 in appearance that it is probable that animals learn to 

 avoid them. Strophanthus, in addition to the poison 

 (^StropJiantJiifi), has a very hard woody envelope formed 

 of the carpel wall which protects the young seeds. In 

 one species there is a curious covering of woolly fringes 

 which is probably intended to keep off insects. The 

 Calabar Bean, Crab's Eyes or JecLuirity and other poison- 

 ous seeds are also very conspicuously and distinctly 

 coloured. Tropaeolum seeds are doubly protected, both 

 by the bitter taste and by their very peculiar wrinkled 

 appearance, which probably resembles particles of the 

 ordinary soil in which they would be found. The 

 following are typical examples of medicinal or poisonous 

 food-stores : Scilla or Squills (bulbs), Aconite (tubers). 

 Turmeric (rhizomes) and Ipecacuanha (roots). 



Mimicry is an even more unusual mode of protecting 

 the food-stores, but it has been suggested as an 



