LOCALIZED STAGES IN DEVELOPMENT. 119 



ternate arrangement prevails in " bird's-nest " growths. On sickly branches or decrepit, 

 dying trees similar needle-shaped leaves are often produced. I have seen old trees, 

 almost bare stumps, but with the few remaining leaves of the typical awl-form charac- 

 teristic of the young. There is, then, in the Red Cedar a clear case of pathologic local- 

 ized stages which repeat youthful or primitive characters. It is a suggestive fact, as has 

 been pointed out by Emerson ('40) and others, that the acerose ternate leaves seen 

 in the young and localized pathologic parts of the adult Red Cedar are closely like 

 the condition seen in the prostrate Juniper {Juniperus communis L.). This allied 

 species, on account of its awl-shaped, bristly, ternate leaves and prostrate habit, we 

 may suppose to be either a primitive or a degradational species, perhaps more likely 

 the latter. The fastigiate form of ./. communis, or Irish Juniper, has similar ternate 

 bristly leaves. Another species, Juniperus calif or nica Carr., has ternate leaves, but 

 appressed, not elongate and awl-like (Sargent, '91-'97). 



Tlie earliest known fossil cedars from the Cretaceous have acerose, ternate leaves. 

 These ancient, primitive types apparently represent the ancestral form from which the 

 acerose, ternate leaves of the young Red Cedar are derived, and to which the similar 

 leaves of pathologic growths of adults are reversions. Junip)erus communis has retained 

 the primitive acerose, ternate type, or else has reverted to it. Juniperus californica has 

 retained the primitive character of ternate arrangement of the leaves, but has appressed 

 leaves, and in this feature is in accord with the progressive species of the genus. 



Juniperus monospermum. Of Juni2')erus monospermum Engel. I had the oppor- 

 tunity of seeing six seedlings at the Arnold arboretum. The seed were collected in 

 Manitou, Col. All of the seedlings had two cotyledons, succeeded by a whorl of two 

 leaves, again succeeded by whorls of four leaves as in J. virginiana. In five of the 

 specimens, four-leaved whorls continued to the top of the main stem (a few inches only), 

 but the leaves of the lateral branches were all in whorls of threes. In one of the 

 specimens there were three-leaved whorls on the upper part of the main stem, showing 

 a transition similar to that shown in Juniperus virginiana (Fig. 5) . 



Thuya occidentalis. An interesting series of seedling Arbor Vitae {Thuya occiden- 

 toZis L.), was sent me from Beedes, Adirondacks, N. Y., by the kindness of Miss Marian 

 C. Jackson. Only one of these was young enough to show cotyledons and the first suc- 

 ceeding leaves. In this specimen (PI. 22, fig. 84) there are two strap-shaped cotyledons. 

 The first nepionic leaves are a whorl of four leaves, 4 mm. long, alternating in position 

 with the cotyledons, as shown diagrammatically in PI. 22, fig. 84a. The second whorl is 

 also composed of four leaves alternating with the first whorl. Succeeding leaves in this 

 and most specimens are in whorls of two leaves, no four-leaved whorls occurring in later 

 growth, and no three-leaved whorls appearing at any stage. 



