548 



Professor L. C. Miall 



[March 4, 



times the budding is so rapid, that, before a fresh pair of leaves have 

 become free, they have already budded out a second pair, which we 

 may call the grand-daughters of the parent leaf. The pointed end of 

 the leaf, and also the opposite end of the ridge, are raised above the 

 general level, and very marked capillary curves ascend from the 

 general water-level to these points. The free edge of every bud is also 

 raised above the general water-level, and a capillary curve ascends to meet 



Fig. 3. 



D 



Duckweed (Lemna 7?n'nor), magnified. A, single frond ; a, scar of attachment 

 to parent. A ridge extends from a to 6 across the upper surface of the frond, 

 gently subsiding towards h. B, frond, budding-out two new fronds. C, longi- 

 tudinal section from a to 6 (A) showing ascending capillary curves at a and b. 

 D, transverse section at right angles to the last. The margins of the frond in 

 this plane are level with the surface of the water. N.B. — The form of the fronds 

 is somewhat variable. Minor inequalities occur along the margin, but the 

 principal ascending curves, which are also centres of attraction, are at a, h, and c. 



it. Hence, when a number of leaves of duckweed are floating freely on 

 water, they are powerfully attracted one to another at certain points, while 

 at intervening points they are relatively inert. If you take a floating 

 leaf of duckweed, and bring near it a clean needle or a pencil-point, 

 or any similar object, provided that it is not greasy, you will see that 

 the leaf is at once attracted towards the point, but it always turns 

 itself so as to bring one of its ascending curves round to the needle 

 or pencil. We all see in the lantern how readily a leaf of duckweed 

 is made to rotate rapidly by causing a needle-point to revolve round 

 it, without ever touching it. Let us now try to imitate the behaviour 

 of the leaves by some rude models. I have here some elliptical 

 paper floats, cut out with a pair of scissors, and having each of the 

 pointed ends a little turned up. We place these one by one on the 



