Chap. VII. FIEST-FOKMED r.EAVES. 415 



the gorse, or Ulex, is not narrow and spinose like the 

 older leaves. On the other hand, with many Leguiui- 

 nons plants, for instance, Cassia, Acacia lophantha, &c., 

 the first leaf has essentially the same character as the 

 older leaves, excepting that it bears fewer leaflets. In 

 Trifolium the first leaf generally bears only a single 

 leaflet instead of three, and this differs somewhat in 

 shape from the corresponding leaflet on the older leaves. 

 Now, with Trifolium Pannonicum the first true leaf on 

 some seedlings was unifoliate, and on others completely 

 trifoliate ; and between these two extreme states there 

 were all sorts of gradations, some seedlings bearing 

 a single leaflet more or less deeply notched on one 

 or both sides, and some bearing a single additional 

 and perfeet lateral leaflet. Here, then, we have the 

 rare opportunity of seeing a structure proper to a more 

 advanced age, in the act of gradually encroaching on 

 and replacing an earlier or embryological condition. 



The genus Melilotus is closely allied to Trifolium, and 

 the first leaf bears only a single leaflet, which at night 

 rotates on its axis so as to present one lateral edge to 

 the zenith. Hence it sleeps like the terminal leaflet 

 of a mature plant, as was observed in 15 species, and 

 wholly unlike the corresponding leaflet of Trifolium, 

 which simply bends upwards. It is therefore a curious 

 fact that in one of these 15 species, viz., M. Tatirica (and 

 in a lesser degree in two others), leaves arising from 

 young shoots, produced on plants which had been cut 

 down and kept in pots during the winter in the green- 

 house, slept like the leaves of a Trifolium, whilst the 

 leaves on the fully-grown branches on these same 

 plants afterwards slept normally like tl ose of a Meli- 

 lotus. If young shoots rising from the ground may 

 be considered as new individuals, partaking to a certain 

 extent of the nature of seedlings, then the peculiar 

 manner in which their leaves slept may be considered 



