410 BOTANICAL BIOLOGY. 



at Kew, owe to the kindness of Dr. ScUweinfurtli, a collection of speci- 

 mens of plants from Egyptian tombs, which are said to be as much as 

 four thousand years old. They are still perfectly identifiable, and as 

 one of my predecessors in this chair has pointed out, they differ in no 

 respect from their living representatives in Egypt at this day. The ex- 

 planation which Lamarck gave of this fact " may well," says Sir 

 Charles Lyell, " lay claim to our admiration." He attributed it, in effect, 

 to the persistence of the physical geography, temperature, and other 

 natural conditions. The explanation seems to me adequate. The plants 

 and animals, we may fairly assume, were four thousand years ago, as 

 accurately adjusted to the conditions in which they then existed, as the 

 fact of their persistence in the country shows that they must be now. 

 Any deviation from the type that existed then would either therefore 

 be disadvantageous or indifferent. In the former case it would be 

 speedily eliminated, in the latter it would be swamped by cross-breed- 

 ing. But we know that if seeds of these plants were introduced into 

 our gardens we should soon detect varieties amongst their progeny. 

 Long observation upon plants under cultivation has always disposed 

 me to think that a change of external conditions actually stimulated 

 variation, and 'so gave natural selection wider play and a better chance 

 of re-establishing the adaptation of the organism to them. Weismanu 

 explains the remarkable fact that organisms may for thousands of years 

 reproduce themselves unchanged by the principle of the persistence of 

 the germ-i)lasm. Yet it seems hard to believe that the germ- plasm, 

 while enshrined in the individual whose race it is to perpetuate, and 

 nourished at its expense, can be wholly indifferent to all its fortunes. 

 It may be so, but in that case it would be very unliJie other living ele- 

 ments of organized beings. 



I am bound however to confes? that I am not wholly satisfied with 

 the data for the discussion of this question which practical horticulture 

 supplies. That the contents of our gardens do exhibit the results of vari- 

 ation in a most astonishing degree no one will dispute. But for scien- 

 tific purposes, any exact account of the treatment under which these 

 variations have occurred is unfortunately usually wanting. A great deal 

 of the most striking variation is undoubtedly due to wide crossing, and 

 these cases must of course be eliminated when the object is to test 

 the independent variation of the germ-plasm. Hoffmann, whose ex- 

 periments I have already referred to, doubts whether plants do as a 

 matter of fact vary more under cultivation than in their native home 

 and under natural conditions. It would be very interesting if this could 

 be tested by the concerted efforts of two cultivators, say, for example, 

 in Egypt and in England. Let some annual plant be selected, native 

 of the former country, and let its seed be transmitted to the latter. 

 Then let each cultivator select any variations that arise in regard to 

 some given character ; set to work, in fact, exactly as any gardener 

 would who wanted to " improve" the plant, but on a preconcerted plan. 



