LOCALIZED STAGES IN DEVELOPMENT. 107 



Fraxinus anomala. According to Professor Sargent ('91-'97) Fraxinus anomala 

 Wats, is a small tree or shrub which usually bears simple leaves, but occasionally leaves 

 which are trifoliolate or five-foliate. Such compound leaves are doubtless reversions, and 

 appear to be compai'able to the reversionary leaves just mentioned in the White Ash. 

 One is a case of failure to develop the full specific characters in a progressive type, as 

 the other is a case of developing more than the full specific characters in a regressive 

 type; but both are localized ontogenies of a reversionary character. In Mr. Faxon's 

 drawing Fraxinus anomala, in Professor Sargent's Silva, the typical single leaves are 

 rounded, with long petioles, resembling the rounded leaves seen often in seedlings or 

 suckers of the White Ash. The terminal leaflets of compound leaves, and simple leaves 

 on flowering branches, are acuminate as in other ashes. The development of Fraxinus 

 anomala should be interesting. 



Fraxinus pubescens. The seedling of the Red Ash (^Fraxinus i^uhescens Lam.) 

 closely resembles that of the White Ash. The cotyledons are similar, and there are five or 

 six pairs of simple leaves which are oval, elongate. They differ, however, from the sim- 

 ilar leaves of the V/hite Ash in being less acuminate distally, deeper green, and the later 

 simple leaves are finely serrate. While serrations occur on all my specimens, they were 

 from one locality, and other seedlings might not be serrate, as adults vary in this 

 character. The compound leaves appear, as in the White Ash, first as trifoliolate leaves, 

 later with more divided leaves. Leaves formed late in the season's growth, in the Red 

 Ash, show a tendency toward sessile lateral leaflets, as in the White Ash. 



Other Ashes. According to Sir John Lubbock, the seedling of Fraxinus excelsior 

 L. has but one pair of simple nepionic leaves, the second pair being trifoliolate. Both 

 sets are serrate. This species is markedly accelerated in its development, as compared 

 with the Red and White Ash, on account of acquiring compound leaves so much earlier. 



We find that the seedlings of the Red Ash and the White Ash have simple leaves, 

 followed by compound leaves, the lateral leaflets of which are sessile. These features are 

 repeated in suckers of the White Ash. The distal leaflet of adult leaves of both species 

 resembles the simple nepionic leaves, and leaves of late growths tend to reduce the petio- 

 lules in lateral leaflets, as in the young. \n the Black Ash (Fraxinus sambucifolia Lam.) 

 the primitive character of sessile lateral leaflets is characteristic of the adult, but the dis- 

 tal leaflet has a long petiolule as in other species. The same characters exist in the 

 European Ash (Fraxinus excelsior Jj.) , Fraxinus australis Gay, and usually in F. oregona 

 Nutt. In fossil ashes the lateral leaflets are sessile, as in the young of specialized and 

 adult of what in this feature, at least, are primitive species. 



Sassafras sassafras. In Sassafras sassafras Karsten {S. officinale Nees) the seed- 

 ling (PI. 19, fig. 49) retains the fruit in place and leafy cotyledons are not developed. The 



