416 



#, Leaves with stipules. 



Calyx imbricated ..... Cistacea, 536. 

 Calyx valvate. 



Stamens monadelphous . . . Malvaceae, 546. 



Stamens distinct . . . . Tiliacece, 557. 



6, Ovary partly inferior ...... Nyrnphaceae, 520. 



B. Stamens less than 20. 



a, Leaves with stipules; carpels consolidated, 

 o, Placentae parietal. 



Leaves unfolded from spiral coil ' . . Droseraceee, 540. 

 Leaves unfolded straight . . . Violaceae t 538. 



)9, Placentae in axis. 



Fruit with beak . . ... Geraniacea, 572. 

 Fruit without beak. 



Stamens monadelphous ... Qxalidece, 577. 



Stamens opposite petals . . . Ampelidece, 566. 

 b t Leaves without stipules. 



o, Carpels distinct, anthers with valves . . Berber idea, 519. 

 )8, Carpels consolidated. 



Placentae parietal, stamens tetradynamous . Crucifercs, 529. 



Placentae in axis, stamens not tetradynamous. 

 Styles distinct. 



Capsule one-celled, with free central 



placenta Caryophylleae, 541. 



Capsule many-celled . . . Linacece, 543. 



Styles united, leaves dotted . . . Rutacea, 578. 



pick in our walk through a lane a specimen of the common duckweed, or Stitch- 

 wort. The veined structure of its leaves, the prevalence of the number five in its 

 flowers, and its general aspect, prevent any doubt that it is an Exogen. On 

 examining the structure of the flowers, we at once perceive that the stamens are 

 hypogynous ; for we may pull off both calyx and corolla, without detaching them 

 from the disk, on which they are separately inserted. The plant belongs, there- 

 fore, to the sub-class Thalamiflorae. The stamens may be from five to ten in 

 number; it is comprehended, therefore, in the second division (B) of the table. 

 Its leaves are readily seen to be without stipules, and we consequently look for it 

 in the group of orders below b. On examining the carpels, they are seen to be 

 consolidated; and, on cutting across the ovarium, the placentae are found to bo 

 central; it must, therefore, belong to one of the three lowest orders in the table. 

 It cannot be a Rue, since its leaves are destitute of glandular dots; it must, 

 therefore, be either one of the Linaceae or of the Caryophylleae ; the most obvious 

 difference between which is usually in the structure of their calyx, as formerly 

 explained (. 543); but the most constant difference is that which is specified in 

 the table as existing between their fruit. When the plant has thus been referred 

 to its proper order, the whole of the general account given of that order will be 

 found applicable to it, and to other species closely allied to it. 



