580 Home Natcre-Study Course. 



LESSON XLII. 



THE TUBER. 



Purpose. — To lead the pupils to see for themselves the seldom noticed 

 peculiarities of this familiar food-plant. 



Material — One or two potatoes for each pupil, preferably of dif- 

 ferent varieties — long, globular, and with different colored skins. 

 Observations by pupils. — 



1. Where does the potato grow? 



2. Has the potato a smooth surface like an apple? 



3. Are the " eyes " distributed regularly on its surface or scattered 

 hap-hazard ? 



4. Where are the eyes most numerous, on sides, near the stem, or at 

 the opposite end? 



5. Is the skin thin and paper-like, or rough and netted? 



6. Where do the sprouts start when the potato begins to grow? 



7. Are any rootlets attached to the potato as to beets and turnips? 



8. Of what is the flesh of the potato mostly composed? 



Facts for teachers. — However differing in size, shape or color, all potatoes are 

 alike in having small pits or " eyes " on their surface, fewest near the stem and 

 very numerous at the opposite or " bud " end. They are arranged in a tolerably 

 regular spiral around the tuber, like leaves on a stem. If the potato is allowed to 

 sprout we discover that each eye is a leaf-bud and from it the growth springs when 

 potatoes are planted. Now, leaves only grow on stems and so we must conclude 

 that the potato is an underground stem, so modified for the storage of plant-food. 

 Man has taken advantage of this tendency of the potato plant to store up food 

 for future growth, and by careful choice and cultivation has enormously increased 

 it, making it feed many millions of men and animals. Its skin is a thin layer of 

 corky substance just as other stems are and in some kinds with slightly rough or 

 netted skins the bark-like character is plainly seen. Often dots or freckles show 

 on the skin and beneath it, like the lenticels on the bark of young trees. Beneath 

 the corky layer is another, which if the tuber pushes up into tlie sunlight in 

 growing, can develop the green substance, usually found in the leaves ; this renders 

 it acrid and unfit to eat; therefore, potatoes should never be left long exposed to 

 the sun when digging. Within this second layer and forming the greater part of 

 the potato is a great store of starch. 



Rootlets are never attached to the tubers of the potato, but to the main root- 

 stem of the plant itself. 



LESSON XLIII. 



PLANTING. 



Purpose. — To show the children how to grow the valuable plant and 

 to teach something of its great share in contributing to the country's 

 wealth. 



Suggestions for teacher. — Strive to make the young gardeners understand that 

 poor seed is not likely to produce fine crops. Every eye on a potato will develop a 

 leaf-bud and put forth rootlets, even though it is a mere scrap of peeling. But 

 experiments have shown that the yield is much smaller, both in size and quantity, 

 from seed so small that the young plants have no store of starch to feed upon 

 until alile to manufacture their own in the new, green leaves by the aid of the heat 

 and light of the sun. Farmers have a saying, " Plant halves when seed is cheap, 



