74 



DICOTYLEDONS 



The seedlings show a peculiarity, which we have already 

 noticed in the leaves of the Bean (see page 34). They fold iip 

 tlieir seed-leaves face to face at sunset, and expand them when 

 daylight comes again. We have learned the importance of these 

 movements, but here the folded seed-leaves seem to afford protec- 

 tion to the young shoot between them, which being very tender, 

 might be liable to damage owing to the reduction of temperature 

 during the night. 



3. The Stalk, as well as the leaves, are covered with numer- 

 ous bristly hairs as a protection against animals. The hollow, 

 live-edged stem is succulent and long, and, hence, not able to stand 

 upright. It, therefore, lies prostrate on the ground or climbs 

 with tlie help of its tendrils. (These wiry appendages rising 

 from near the axils of the leaves are probably metamorphosed 

 bracteoles supporting, as they do, the axillary flowers.) The 

 ends of these tendrils move slowly, but continuously round, like 

 the hands of a watch. The time they require for one circuit 

 ditt'ers and depends chieliy on the temperature. If we put a 



little stick in the way of 

 the moving tendril, Ave 

 can notice the following. 

 A few hours after the tip 

 of the tendril touches the 

 stick, it will have formed 

 a sling round it. Some 

 time later we shall tind 

 the stick wound round 

 several times, and in the 

 course of a few days the 

 part of the tendril between 

 its base and the stick will 

 l)e coiled up like a cork- 

 screw. The coiling is 

 always accompanied by 

 tu'isfinf/, and since the 

 base and tlic md of the tendril are fixed before these processes 

 take place, the directions in whicli the tendril coils round must 



Fig. 7 



A twij,'' f)f Liiijd aculangulti witli 

 tendril. 



