CAPEIFOLIACE^ 



219 



S. nigra (Elder) has the flowers honeyless, sweet- 

 smelling, homogamous, and united in large corymbs, 

 which makes them very conspicuous. They are, how- 

 ever, not much visited by insects, and the anthers open 

 outwards, but the stigma comes in the fall line of the 

 pollen from at any rate one of the anthers. The flowers 

 are principally visited 

 by flies. The scales ^^ 



protecting the bud are 

 petioles ; the outer 

 ones are very small ; 

 the third pair often 

 terminate in more or 

 less rudimentary 

 leaves. 



TIta l->arlr nf tVip ^^'^- ^^^- — Lenticel from a hTimch o{ Sambucus 

 XHti UdlK Ui LUt; ^j^.^^^^ jjj ^^g summer of the second year. 



e, epidermis ; I, loosely arranged cork cells 

 forming the Icnticel ; Ic, parenchyma of 

 cortex ; pi, formative layer by the transverse 

 division of the cells of which the lenticel is 

 formed ; q, formative layer giving rise to the 

 ordinary closely packed cork cells. 





younger shoots is a 



good subject for the 



study of lenticels. 



These are oval spots 



where the cork cells 



are loosened and separated sufiiciently to allow free 



passage of air, as shown in the above figure (Fig. 145). 



Lenticels replace the stomata of the young green shoots 



as respiratory organs. 



Viburnum 



We have two very distinct species. V. Opuhis has 

 three- to five-lobed glabrous leaves, and red berries ; V. 

 Lantana, entire leaves, downy underneath, and purplish- 

 black berries. The honey is free-lying, or half concealed, 

 and F. Opulus has nectaries on the leaf-stalks. 



V. Opulus (Guelder Eose) (Fig. 146).— This is the 

 wild form of the Guelder Eose. As in many of the 

 Umbelliferse the outer flowers are larger than the central 

 ones. In this species, indeed, they serve merely to make 

 the flower-head more conspicuous, for they have neither 

 stamens nor pistil, as Sprengel long ago observed. The 

 flowers are homogamous. They are visited by bees for 



