August 3, 1882] 



NATURE 



!25 



habitually fertilised by bees, and the same is partially 

 tiue of many of the other species. All of them are adapted 

 to a high class of insect visitors. 



Other families of regular Corolliflora must be glanced 

 at more briefly. Among the Gentianacea, the less ad- 



16. — Section of Daisy 



white, tipped 



advanced types, like the simple Chlora perfoliate* and 

 Limnanthemum nymphaoides, are yellow, perhaps by 

 reversion ; but Menyanthes trifoliata, a slightly more de- 

 veloped ally of Limnanthemum, has white blossoms, 

 tinged outside with red ; Erylhrcra centaurium, with a 

 divided calyx and the cells of the ovary imperfectly 



Fig. 17. — Flower of Sage, bright blue 



united, is pink ; and the true gentians, Gentiana versa, 

 G. campestris, G. nivalis, &x., with a tubular calyx, long 

 throat, and sometimes fringed hairs to the tube, are bright 

 blue. In Apocynacea, we have the highly developed 

 periwinkles, Vinca major and V. minor, normally blue, 

 though pink and white varieties or species are also culti- 



—Gagca lutea, yellow: simplest type of lily. 



vated. In Plumbaginea: we have the bluish purple sea- 

 lavender (S/atice Limonium) and the pink thrift {Armeria 

 vulgaris). Other families with special peculiarities will 

 receive notice later on. 



It is necessary, however, here briefly to refer to the 



great family of Composi/a?, some of whose peculiarities 

 can only properly be considered when we come to inquire 

 into the phenomena of relapse and retrogression. Never- 

 theless, even at the present stage they afford some excel- 

 lent evidence. In certain ways they may be regarded as 

 the very highest race of flowering plants. Not only are 

 their petals united into a tubular corolla, but their 

 blossoms are compounded into large groups of a very 

 attractive sort. Each flower-head consists of a number 

 of small florets, crowded so as to resemble a single 



Fig. 19. — Fritillary, purple, spotted with white and red; developed type of 

 lily. 



blossom. So far as our present purpose is concerned, they 

 fall naturally into three groups — Jussieu's old-fashioned 

 sub-orders of Ligulatce, Cynaroidea:, and Cory mbif era: , 

 which are quite sufficient for all ordinary objects of 

 botanical study. 



We can only examine the last-named tribe at present, 

 whose central florets, as a rule, are bright golden ; a fact 

 which shows pretty certainly that they are descended 

 from a common ancestor who was also yellow. Moreover, 

 these yellow florets are bell shaped. But the outer florets 

 are generally sterile ; and instead of being bell-shaped, 



Fig. 20.— Spotted Orchid, purple with white patches : type of highly He 

 loped bilateral monocotyledons. 



they form a long ray ; while their corolla is at the same 

 time much larger than that of the central blossoms. In 

 short, they are sterilised members of the compound 

 flower-head, specially set apart for the work of display ; 

 and thus they stand to the entire flower-head in the same 

 relation as petals do to the simple original flower. Just 

 as the petal is a specialised and sterilised stamen told off 

 to do duty as an allurer of insects for the benefit of the 

 whole flower, so the ray-floret is a specialised and steril- 

 ised blossom told off to do the self-same duty for the 

 benefit of the composite flower-head. 



