FLORA OF PENNSYLVANIA. 



SERIES I. 



PHJSNOGAMIA, OR FLOWERING PLANTS. 



Plants composed of cellular tissue, woody fibre, ducts, 

 and spiral vessels, bearing proper flowers, with stamens and 

 pistils, and producing seeds which contain an embryo, radicle 

 and cotyledons. 



Class 1.— EXOGENS OR DICOTYLEDONS. 



Stems composed of distinct bark and pith with an inter- 

 vening layer of woody fibre and vessels, increasing in diameter 

 by the annual deposition of new layers between the qldwood 

 and the bark, which are arranged in concentric zones and 

 traversed by medullary rays. Leaves mostly with reticula- 

 ted veins, and falling off by an articulation. SEPALS and 

 petals in Jives and/ours, and very rarely in three*. EfilBB vo 

 with two or more cotyledons. 



Sub-glass 1. — Angiospermous Exogens. 



Ovules produced in a closed ovary, and fertilized by the 

 action of pollen through the medium of a stigma. Emek vo 

 with two cotyledons, 



Division 1. — Polypetalous Exogens. 

 Floral envelopes consisting of distinct petals and sepals. 



Order 1. RANUNCULACEJE .— Crowfoot Family. 



Herbaceous plants, occasionally climbing— rarely shrubs, with an acrid colorless 

 juice, awl usually palmalely or ternatdy lobed or divided leaves, without siipidts, .>ihr~ 

 ruic, with half-clasping petioles. 



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