The induction, development, and heritability of fasciations . distal ends of the medullary rays, the latterin older stems become fan-shaped. This condition recalls that observed inCeltis and in Prosopis. The chlorenchyma is increased in amount by the-activity of the cork-cambium also. Periderm is to be seen in stems 9 diameter. It is formed by the subepidermal phellogen, which also givesrise to phelloderm that contains chlorophyll. In the older stems the chloro-phyll band is about one-half periderm and one-half primary cortex. The chlorophyll early disappears from the woody cylinder. In
The induction, development, and heritability of fasciations . distal ends of the medullary rays, the latterin older stems become fan-shaped. This condition recalls that observed inCeltis and in Prosopis. The chlorenchyma is increased in amount by the-activity of the cork-cambium also. Periderm is to be seen in stems 9 diameter. It is formed by the subepidermal phellogen, which also givesrise to phelloderm that contains chlorophyll. In the older stems the chloro-phyll band is about one-half periderm and one-half primary cortex. The chlorophyll early disappears from the woody cylinder. In a branch9 mm. in diameter it could be found in neither pith nor wood, and inbranches 2 cm. in diameter it was confined to the outer portion of the cortexand did not appear to be functional. The following measurements were taken: Distancefrom tip. Diameterof branch. ^%m. mm. -7^20 •5 4 - 35 5-5 — 50 90 •35 120 20 Width ofcortex. Width of Depth of chlorophyll i chlorophyll band. band. 415498780107911621660 48 So PARKINSONIA. 23. I I a U^^M I// ^c O A W ^^^. ^^^^^ PARKINSONIA ACULEATA, P. MICROPHYLLA, AND P. TORREYANA. (Plate 4 and figs. lo and ii.) Parkinsonias are small trees which occur in this vicinity in habitats thatnsually are distinct. P. aculeata is found native on the lower slopes of the Coyote Mountains,about50 miles west of Tucson,but is cultivated in of the city. occurs onTu manioc Hill and onthe low, dry hills in thewestern portion of theLaboratory domain. is growing- inthe wash at the westernbase of Tumamoc three species aregreen in all parts, fromwhich the commonname, pah verde, is de-rived. P. aadeata andtorreyana carry moreleaf-surface, or at leastlarger leaves, than mi-crophylla, in which theyarc extremely small. Ineach species portions orall of the leaves fall awayduring unfavorable sea-sons . The general struc-tural relations of thestem do not need specialnotice; they will be ap-pa
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