THE HIGHER DICOTYLEDONS. 359 



which it may then carry to the stigma of a younger 

 flower. 



In Rhinanthus (Yellow Rattle), Pedicularis (Lousewort), 

 Melampyrum (Cow- wheat), and Euphrasia (Eyebright) we 

 get a "loose-pollen mechanism." The stamens lie under the 

 upper corolla-lip, and the four anthers are close together and 

 usually connected by interlocking hairs in this fashion : 



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so as to form a " pollen-box." The pollen is dry and 

 powdery (like that of wind-pollinated flowers), and when a 

 bee enters the flower it rubs against the lower side of the 

 " pollen-box " and receives a shower of pollen on its head. 



362. Potato (Solanum tuberosum). Examine tubers and 

 also whole plants (freshly dug up) ; plant tubers in soil and 

 in sawdust, keeping some in darkness and others in the light. 



Since the tubers themselves can be at once obtained at any 

 time of year, we will take them first. Do any of the tubers 

 show at one end a stalk or the withered portion of a stalk ? 

 Notice the " eyes " : each eye is a small outgrowth sunk in a 

 pit on the surface of the tuber. Carefully examine one of the 

 larger eyes : is it a solid body, or does it bear any appendages ? 

 What do you think the eye is ? Are the eyes scattered all 

 over the tuber uniformly, or are they more numerous at one 

 end of the tuber? Can you make out that the eyes are 

 crowded at the end furthest from the remains of the stalk 

 which attached the tuber to the parent plant ? If so, we may 

 call one end the " eye end " or " bud end " or " growing end," 

 the other the " stalk end " or " barren end." Have the eyes 

 any definite arrangement on the tuber, or are they scattered 

 anyhow over its surf ace ? 



Try to determine the position of the eyes on a Potato 

 tuber by fixing a pin in each eye and joining the pins by a 

 piece of thread. The eyes are arranged in a spiral, the sixth 

 eye being hi a straight line with the first; the thread in going 

 from the first to the sixth eye goes around the tuber twice. 

 Compare this arrangement with that of the buds on an Oak 

 twig and of the leaves on a Wallflower. 



