348 Excerpta Botanica. 



falciform, or demi-lanceolate, or oblongo-lanceolate. Accord- 

 ing to Willdenow and Reichenbach, one of its distinctive cha- 

 racters was the tripartite involucre ; but an examination of a 

 large quantity of the fruit has demonstrated that this is only 

 an accidental variety which occurs also in C. Avellana, and 

 which is very much rarer than the normal condition, in which 

 the involucre is divided to its base into two nearly equal seg- 

 ments. Another variety, much more common both in Co- 

 lurna and Avellana, has the involucre divided only on one side 

 down to its base, as in that of Carpinus. 



The nut, as in all the species, is either more or less com- 

 pressed, or subcylindrical, or obscurely 3- or 5-gonous, some- 

 times subglobose, sometimes obovate, oval, ovoid or oblongs 

 whilst in size it is equally variable. The number of fruits 

 borne on each peduncle affords no distinctive character, being 

 in all the species either solitary or aggregated, from 2 — 7 or 

 rarely more. 



The male catkins of C. Colurna are generally longer than 

 those of its congeners, but in other respects their structure is 

 similar. This is not the case however with the fertile flowers. 



The most variable organs of Corylus are undoubtedly the 

 leaves and stipules ; and their different modifications of form, 

 size, and pubescence are so inconstant on each individual, as 

 to render it vain to employ them even as characters of va- 

 rieties. 



The leaves of most species are generally suborbicular or 

 ovali- orbicular, though frequently oboval, oval, oval-oblong, 

 elliptico-oblong or oblong ; in general they are suddenly termi- 

 nated in an acute, more or less elongated point ; less frequently 

 they are obtuse or gradually tapered into a point. Their base 

 is cordate (sometimes slightly so, sometimes more or less 

 deeply so) ; less frequently rounded, rarely pointed, some- 

 times nearly equal, and sometimes more or less unequal. 

 Their margins, from base to summit, are doubly or unequally 

 dentate, or crenulate, or jagged, often moreover more or less 

 strongly angular or incised, or sometimes even pinnatifid; 

 sometimes plane, and sometimes undulated or crisped. Both 

 surfaces are sometimes more or less pubescent, sometimes so 

 only on the under surface ; sometimes, though very rarely, 

 glabrous on both surfaces, except the axils of the nervures of 

 the inferior surface, which are always more or less strongly 

 bearded. The petiole is cylindrical or obscurely trigonous, 

 not channelled, more or less short, hairy, pubescent, hispid or 

 glabrous. The hairs or bristles sometimes glandulose, some- 

 times not so. These variations of pubescence occur also on 

 the stipules, young shoots and peduncles. 



