138 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



the other it is the seed of one species which, "between the sowing of 

 it and the germination, mysteriously changes to that of another 

 species. 



There is, however, a phase of transformation in plant life that 

 runs parallel to the metamorphoses of lower animals. This has 

 become generally known only recently, and by means of the com- 

 pound microscope as applied to the making out of the life histories 

 of ferns, liverworts, and other fiowerless plants of lower organization. 

 As illustrated in these plants, this kind of individual metamor- 

 phosis could never have become known to the nature students 

 of antiquity, or even to those of the earlier modern epoch, owing 

 to their lack of the necessary optical aids. But somewhat analo- 

 gous metamorphoses take place in the individual life histories of 

 certain higher plants, even of trees; and this fact is not so com- 

 monly known as it ought to be. In the family of the Mimosacese 

 there is a considerable list of trees which only in the state of seed- 

 lings of a few years old exhibit the usual delicate fern-like doubly 

 pinnated foliage of their family. Before the trees are old enough 

 to flower they have divested themselves of every trace of that 

 kind of leaf and are clothed instead with very narrow, simple, 

 entire, firm and almost leathery organs, in cut somewhat recalling 

 willow leaves, or perhaps better compared to those of mistletoe. 

 Now it will not be in the least to the discredit of a circle of ex- 

 perienced and quite skilful botanical amateurs of the Northern 

 Hemisphere if, placing before them two branches of such an acacia, 

 one from the ferny-leaved young tree, the other from the mature 

 tree with its stiff phyllodes like mistletoe leaves, and stating that 

 these two branches represent one and the same species of Australian 

 acacia, the whole circle of them suspect at first that I may be 

 jesting. Some of the Australian eucalyptus species undergo as 

 complete a metamorphosis in the individual, with this difference 

 that the adult tree, at least in the earlier stage of maturity, ex- 

 hibits both phases of branch and foliage ; the lower and fiowerless 

 portion of the head of the tree seeming to represent one genus, the 

 middle and upper branches — those that have the flowers and 

 fruits — seeming as if they must be those of another genus, or even 

 of another family. It is quite as if the tree at a point just below 

 midway of its axis, had become by grafting from that point upwards 

 a tree of another genus. 



Of these changeable acacias and eucalypts the ancient Greeks 

 of course knew nothing; but they were familiar with a similar case, 

 that of what is known in very modern botany as Hedera Helix, 



