ON THE MECHANISM OF LEAVES, ' 2 



resemble the ash, they are governed by a very different 

 species of mechanism : they have a swellinuj down each side 

 of the stalk, in which the spiral wire runs in a groove (see 

 fig. 2, h b) which corresponds with the sort of knob round 

 which the wire of each leaf is turned ; communicating all 

 the way with a knot and pulley till it reaches the protector 

 at c c, fig. 1. 



The management of the galia, and most of those plants, Mechanism 

 the stalks of which enlarge where the leaves meet, is con- ^^^ socket. 

 trived in a curious manner, v/ith a sort of mechanism 

 consisting of a ball and sockets No part of a plant (the 

 seed excepted) has given me so much trouble as this ; 

 having found two sorts of balls in vegetable life, and con- 

 founded the two together, viz. the ball and excrescence in 

 trees, and the ball continually found appertaining to the 

 mechanism of plants. I have at last learned to distinguish 

 them. Of those in trees I shall soon give a description, 

 when entering again on the subject of the wood in plants; 

 which will develope many hidden secrets, that ought to be 

 explained, and illustrate many things that may h«.ve ap- 

 peared contradictory. Respecting the ball, which forms a 

 part of the mechanism in plants, each stem has one, on 

 which it turns like the knee of a quadruped : but, to see the 

 ball, the plant must be taken at a very early age, for it is 

 the first part that decays, and in the phaseolus vulgaris 1 have 

 known it gone before, the flower disappeared ; and I have 

 oftei^seen five or six stems turn in one collected set of joints. 

 When old they stitfen, and a sort of matter fills up the 

 instertices of the sockets. They then become immovable; 

 but before this, if you move the stem, you u^ay see thetn 

 turn, but cannot turn them yourself without breaking the 

 spiral wire. See fig. 3, and a section at fig. 4. This speci- 

 men will at least discover the manner in which the spiral 

 wire is conveyed from one ball to another^ communicating 

 its influence, and-spreading its power from stem to stem. 



I must now correct a mistake 1 before made in saying, 



that there was no spiral wire in the ericae. It is so diminu- The erice 



tivc, and lies so low in the "roove, that I overlooked it. P°^^^^*^^® 

 » •' spiral wire- 



The leaves of the heaths, though very sessile, still possess a 



motion to and from the plant. See fig. 5, c c. They are 



B 2 placed 



