1886.] Sir John Liibhock on the Forms of Seedlings. 517 



WEEKLY EVENING MEETING, 



Friday, May 21, 1886. 



The Duke of Northumberland, K.G. D.C.L. LL.D. President, in 



the Chair. 



Sir John Lubbock, Bart. M.P. D.C.L. LL.D. F.R.S. M.B.L 

 The Forms of Seedlings : the causes to which they are due. 



Sir John Lubbock commenced, the lecture with some general remarks 

 on the innumerable types of foliage among mature plants and the 

 causes to which we might refer their various forms, the breadth of 

 some and narrowness of others, the differences of position, the dif- 

 ferences of length in conifers, &c. He said that these considerations 

 had led him to study the cotyledons or first leaves of seedlings. 

 Cotyledons do not present such extreme differences as leaves ; never- 

 theless, they afford a very wide range. Some are broad, some narrow, 

 some are long, some short, some are stalked, some sessile, some 

 lobed, some even bifid or trifid. At first sight, these differences seem 

 interminable, and it might appear hopeless to attempt to explain them. 

 Sir John Lubbock, however, pointed out, as regards many species, 

 taking especially the commonest plants, such as the familiar mustard, 

 and cress, the beech, sycamore, pink, chickweed, &c., the conditions 

 of their formation and growth, and it is beautiful to see the various 

 reasons to which the differences are due, gradually unfolding them- 

 selves ; the same result being sometimes brought about by very 

 different circumstances, emargination of the cotyledons, for instance, 

 being due to at least six different causes. He mentioned one curious 

 peculiarity in the seedling of a species allied to our common mistletoe. 

 It is a parasitic species, and its fruit, like that of the mistletoe, is 

 somewhat viscid, so that it adheres to any plant on which it falls. 

 But, even if it reaches the plant on which it grows, it may light on 

 an unsuitable position — say, for instance, a leaf. What then happens ? 

 The radicle elongates for about an inch and then developes on its tip 

 a flattened disc, which applies itself to the plant. If the situation be 

 suitable, there it grows ; if not, the radicle straightens itself, tears the 

 berry from the spot where it is lying, curves itself, and then brings 

 the berry down on to a new spot. The radicle then detaches itself, 

 curves in its turn, and thus finds a new point of attachment. We 

 are assured that this has been seen to happen several times in succes- 

 sion, and that the young plant thus seems' enabled to select a suitable 

 situation. 



The form of the cotyledons, or scedleayes, depends greatly on that 



