DICOTYLEDONS 93 



side of the seed, and say to what it corresponds. Are 

 the chalaza and micropyle close together, as in the bean, 

 or at opposite ends of the seed ? 



Sketch the kernel, or embryo, without opening it, as it 

 appears under the lens. Notice the irregular fold or 

 groove down one side that divides it into two nearly equal 

 parts. Label these cotyledons. Observe the complicated 

 way in which they are folded. Try to imitate it with a 

 piece of paper. Would any other way of folding fit them 

 so snugly into the seed coats? Straighten them out as 

 well as you can and sketch them. Which are most leaf- 

 like, the cotyledons of the bean or the cotton ? Are either 

 of them at all similar in shape to the foliage leaves of their 

 respective plants ? How do they compare in size relatively 

 to the size of the respective seeds ? Which are best fitted 

 to perform the office of true leaves ? 



In seeds like the pea and bean, where the cotyledons 

 are too thick and clumsy to do well the work of true leaves 

 the young plant will need a well-developed plumule to 

 begin life with, but where the cotyledons are thin and 

 leaflike, as in the cotton, and to a less degree in the pump- 

 kin and squash, and capable of developing quickly into 

 true leaves, there is generally no plumule formed in the 

 embryo. 



123. The Castor Bean. Lay a castor bean on a sheet 

 of paper before you with its flat side down ; what does it 

 look like? The resemblance may be increased by soak- 

 ing the seed a few minutes, in order to swell the two little 

 protuberances at the small end. Can you think of any 

 benefit a plant might derive from this curious resemblance 

 of its seed to an insect ? 



Sketch the seed as it lies before you, labeling the pro- 

 tuberance at the apex, caruncle. The caruncle is no 

 essential part of the seed, but a mere appendage devel- 

 oped by various plants, the use of which is not always 

 clear. What appears to be its object in the castor bean ? 

 It may occur on any part of the seed, though it generally 



