THE HIQHEB DICOTYLEDONS. 367 



how rain-water falling on the leaves runs down the midrib to 

 the tap-root, in which is stored the food that enables the 

 plant to live from year to year. The Dandelion is really an 

 evergreen plant, since it is never without leaves. 



In a dug-up plant note the long tap-root, which is usually 

 blackish outside and white inside ; cut across the root of a 

 plant and note that soon a healing-tissue (" callus ") forms 

 over the cut surface, from which arise new shoots. It is not 

 easy to tell, by inspection, where root ends and stem begins ; 

 the stem remains very short, covered by the leaf -bases, and 

 each year it produces a bud for the shoot's further growth, 

 while the root contracts (as in so many other " ground- 

 hugging " plants, e.g. plants with runners, rosette-forming 

 short stems, underground stems, bulbs, corms, or thick food- 

 storing tap-roots) and draws the stem down so that it never 

 comes above the soil. What do you suppose is the use of 

 the bitter juice contained in the Dandelion tap-root along 

 with the reserve-food ? 



The flowers, which appear in early summer but may be 

 found (in south England and in sheltered places elsewhere) all 

 the year round, are in solitary heads, each head on a long or 

 short stalk. The stalk is smooth and hollow ; when cut it 

 gives milky bitter juice (also found in other parts of the 

 plant) which turns brown on exposure to the air. Note the 

 numerous (100 to 300) small flowers crowded on the flat 

 expanded circular top of the flowering stem, each flower 

 being inserted in a small pit. Where are the youngest 

 flowers at the centre or at the outside of the disc? By 

 comparing heads of different ages you will find that the 

 flowers open successively from outside to centre, so that the 

 head resembles an umbel (e.g. Cowslip, Ivy) in which the 

 flowers have no stalks (or very short ones) and are seated on 

 the disc-like end of the flowering axis. Note the double 

 circle (involucre) of narrow green leaves (bracts) around the 

 head. 



How do the outer bracts differ from the inner ones in 

 form, position, and function ? Does either series appear 

 to perform any function besides that of protecting the very 

 young flower-head before any of the flowers open or the 

 flowering axis grows up ? Why does the inner series remain 

 erect, though the outer bracts bend downwards ? 



