No. 431.] STAGES IN PLANT GROWTH. 873 
second nepionic leaf is trifoliolate, as well as several following 
ones. Then the number of leaflets increases to five, and in the 
full-grown plant becomes seven. In the first spring growth the 
first leaf, especially upon the lower or weaker parts of the plant, 
is very often trifoliolate, like the second nepionic leaf in all 
cases and like the first in some. In some cases, however, a 
simple leaf may be found, but rarely.. When it does appear, 
it may be compared to the simple leaf seen in the first nepionic 
leaf of Fig. 1. After this trifoliolate leaf in the spring growth 
of the adult is one of five leaflets, then usually five leaflets until 
the flowering stage. Then the number drops by the same steps 
that it increases, but in the reverse order. Going toward the 
flower, leaves are encountered with five, then three leaflets, until 
finally just below the flower there is a simple one. Here, then, 
are repeated the exact steps by actual count of the stages of the 
seedling in the early spring growth, and as exact a reversal 
of the same stages beneath the flower. The same is true of 
Rosa lucida and other species (Pl. IV, Fig. 3). 
Although these examples given might be multiplied almost 
without number, they will do to illustrate several general prin- 
ciples which may be drawn from them. The various conditions 
are more or less combined in any actual case, as they often 
are in such problems, but the effect of each may be noted 
nevertheless. 
First, the relation between the occurrence of the earliest 
stages and the age of the plant. The plant coming up the 
second year, other conditions being the same, seems to be more 
primitive in its first characters than older and stronger plants. 
It therefore repeats more stages in arriving at the typical form 
than older individuals. The case of Viola pedata illustrated 
this, the young plants of the preceding year being the ones in 
which the earliest stages were noticed. In some plants, how- 
ever, the typical leaf of the species is not reached for several 
years. The young trees of Carya alba Nutt. the shagbark 
hickory, have when very young — the second year, for example 
— only single and trifoliolate leaves, and it is some time before 
the number rises to five leaflets. The typical one of seven 
leaflets does not appear until quite a late period. 
