222 COMPENDIUM OF GENERAL BOTANY. 



Sympetalce, according to whether the petals of the corolla are 



free or united. To 

 the former belong 

 the CrucifercB, 

 Ranunculaceoe, and 

 fiosacece; to the 

 latter the Ldbiatce, 



FIG. 149. Carum Gentianacece, Sola- 

 carvi. Diagramatic ~ 



cross-section of a ncwew, Composite. 



148,-Seed of Daneu. 61 



, 



Carola (carrot). oil-glands near 6 and e\ ceminS" " SVmpet- 



(After Berthold and Landois.) d and '' Primary ribs; e O J 



secondary ribs with oil- a l oll g ' ' flowers.) 



(A "En!]o^ er ) th ld and We will now 



consider the structure and function of the nectaries, and then pass 

 to the discussion of the andrcecium and gyncecium. 



As already indicated, the nectaries serve to secrete a honey-like 

 substance called nectar. This secretion attracts insects, which feed 

 upon it, and by their movements on lighting and attempting to 

 secure the nectar cause the pollen to adhere and alight upon them, 

 to be carried to other plants (of the same* species) for the purposes 

 of cross-fertilization. The nectaries are morphologically different 

 in different plants. In Alchemilla vulgaris they are located in 

 the calyx, very frequently they are located in the petals, forming 

 the spurs of orchids, Ranunculacece, etc. In Caltha palustris 

 they are located near the base of the ovary ; in Cerastium, near the 

 base of the filament ; among many of the Liliacece they occur in 

 the septa of the ovaries, and are known as septal glands. Finally, 

 there are nectaries formed by special structural modifications, such 

 as those of Parnassia palustris and Musa paradisiacal 



Not every insect can secure the nectar of any flower. Certain 

 insects are especially adapted to certain flowers in order to bring 

 about cross-fertilization. The depth of the floral tube and the spur 

 corresponds to the length of the proboscis of the visiting insect. 

 There are also protective arrangements to prevent the visit of use- 

 less or harmful insects. Such are the hair-cells and scaly structures 

 in the corolla, which sometimes makes access to nectaries difficult or 

 impossible (Labiatce, Asperifolice) ; also the so-called * ' masked ' ' 



1 Studied more in particular by W. BEHRENS, Flora, 1879. The above state- 

 ments are based upon the investigations of this author. 



