LOCALIZED STAGES IN DEVELOPMENT. 115 



cause existed. When young seedling plants throw out lateral branches close to the ground, 

 it is found that such branches for a certain distance are clothed with primary leaves, as is 

 the vertical axis at the area where they originated. This is in accord with what has been 

 observed in many other cases ; namely, that branches from nepionic areas are character- 

 ized by nepionic leaves, as in Ampelopda tricuspidata, Negundo, ashes, oaks, Areca, etc. 



In the Pitch Pine, then, we find nepi(mic characters repeated in localized parts, either 

 as branches from the nepionic area, or abnormal growths from any portion of the j^lants, 

 but especially from stumps and young trees wliich have lost their leader or other prom- 

 inent branch. 



While in normal growth the Pitch Pine loses its primary leaves very early, Sargent 

 ('01-'97) says they may be retained for several years in the nut pines. In Prnus quadrl- 

 foJia he says that after five or six years the primai-y leaves are shorter and begin to bear 

 leaf-clusters in their axils. At Shady Hill nurseries plants of Pinus densijlora and P. 

 massoniana, a foot or more in height, were seen which bore primary leaves with axillary 

 leaf-clusters on all parts of the plants. 



Pixrs STEOBUS. In the White Pine {Pinus strohitsli.) , seedlings (PL 21, figs. 78-80) 

 have from seven to ten cotyledons, in specimens examined at the Arnold arboretum and 

 Shady Hill nurseries. Out of eleven seedlings, four have seven cotyledons, two have 

 eight, two have nine, and three have ten cotyledons. The cotyledons are large and strong, 

 as in the Pitch Pine, which they resemble. There is one marked ditference, however. In 

 the White Pine the cotyledons are roughly triangular in section, and bear on their inner 

 angle or ridge, also occasionally on their outer angles (Fig. 7'Ja) , fine saw-like teeth similar 

 to the teeth of nepionic and adult leaves of this and other species. Similar teeth exist on 

 the cotyledons of Putus montlcola Dougl. and Lamb, as observed at the Arnold arboretum. 

 Serrations of the cotyledons of Pinus strohiis are mentioned by Dr. Masters ('91), but 

 have not been dwelt upon before. Such teeth do not exist in the cotyledons of Pinus 

 rigida, P. cembra L., P. resinosa Aiton, or P. imngens Lamb. These teeth of cotyledons 

 may be considered as a case of accelerated development in which features usually appear- 

 ing first at a later stage are shoved l)ack to an earlier, in this case an embryonic stage. 

 Compare with Eucharidimn r/raiidiforum, Figs. 1 to 3, page 103, which during growth 

 acquires nepionic characters in embryonic leaves. The succeeding primary leaves of the 

 White Pine seedling are similar to those of the Pitch Pine, but are retained longer than in 

 that species ; primary leaves are retained in the specimens observed until the plant is from 

 3.5 to 5 cm. in height, the end of the first year's growth. Then (PI. 21, fig. 81) the 

 primary leaves begin to shorten, and bundles of five leaves, characteristic of the species, are 

 borne in the axils of the shortened primary leaves which are soon replaced by small scales. 

 Pi'imary leaves apparently never occur in later normal or abnormal growths of this species. 



