346 Excerpta Botanica. 



scales, and not superposed in two regular series. The brac- 

 teas at the base of the female involucres, far from being always 

 oval or entire, are on the contrary various in form, sometimes 

 entire, and sometimes more or less cut. These bracteas are 

 persistent and accrescent, whilst in the nearly allied genera 

 Carpinus and Ostrya they are deciduous shortly after flower- 

 ing. The female involucres are constantly one- and not two- 

 flowered, not sometimes one- and sometimes two-flowered. 

 They are not aggregated without order, but are always in- 

 serted in pairs in the depressions (fossettes) of a very abbre- 

 viated rachis, each pair being accompanied by a bractea. The 

 limb of the perianth of the female flowers is never completely 

 obliterated, but is always perfectly visible on the young fruit 

 under the form of a subapicular, pubescent, undulated, or ir- 

 regularly denticulate swelling. The inferior flowers of each 

 cluster are almost always abortive, as is also the case with a 

 greater or lesser number of the superior flowers; consequently 

 the fruit borne on one peduncle are very variable in number, 

 and frequently reduced to one or two. Lastly, the fructife- 

 rous involucres are neither always tubular nor always bipar- 

 tite. 



The hybernal flowering, the appendages of the staminiferous 

 scales, the single-celled anthers, the accrescence of the brac- 

 teas of the female flowers, and the hypogeal cotyledons, con- 

 stitute, conjointly with the female inflorescence and the struc- 

 ture of the fructiferous involucre, the chief essential characters 

 by which Corylus is distinguished from the two nearly allied 

 genera Ostrya and Carpinus. In these latter genera the 

 flowering is vernal, the staminiferous scales are without ap- 

 pendages, the anthers two-celled, either completely disunited 

 or at least parted in the middle. The whole, or greater por- 

 tion of the female flowers are fertile, and produced in large 

 pendent spikes. Their accompanying bracteas are fugacious, 

 and the cotyledons are developed into seminal leaves. 



Sectio I. AVELLANA, Spach. 



Involucrum fructiferum inerme, 2-partitum (rarb S-partitu?n, non- 

 nunquam uno latere tantum usque ad basin fissum), subcampani- 

 forme; segmentis inciso-dentatis, v. palmatis. Nux involucro 

 longior v. brevior. 



1. CORYLUS COLURNA, Linn. Wats. Dendr. Brit., tab. 99.— 

 Corylus byzantina, Seb. Mus. 1 . tab. 27. fig. 2. — Corylus byzantina 

 et Corylus Colurna, Hortul. Arborea, corticis stratis exterioribus 

 in lamellas crassas deciduas solubilibus. Involucris fructiferis 

 (ssepissime 2-partitis) nucibus subduplo (plusve) longioribus : 

 segmentis conniventibus, multifido v. multipartito-palmatis. 



