Minnesota Plant Life. 349 



direction. In the same order the lower families may have reg- 

 ular flowers, while the flowers of the higher families have 

 acquired more specialized irregular shapes. The proper ar- 

 rangement of the orders is not one of sequence, but rather the 

 kind of arrangement that is seen in genealogical charts, or in 

 the trunks, main branches, secondary branches and twigs of a 

 tree. Grasses and sedges, for example, represent the perfection 

 of certain lines of development. Orchids represent the per- 

 fection of another line of improvement, and dogwoods occupy 

 relatively another terminal position. Yet it is possible in a 

 general way to regard the plant with two-leafed seedlings as 

 showing a higher type of embryo-structure than the plant with 

 one-leafed seedlings, and when the orders of plants are discussed 

 in sequence, the former group is considered, as a whole, subse- 

 quent to the latter. On this account, however, it should not 

 be supposed that willow flowers are of higher structural type 

 than orchid flowers, for orchids are among the most perfected 

 of plants with the lower type of embryo, while willows are 

 among the least perfected types with the higher kind of embryo. 

 In general, that higher class in which the petals are blended into 

 corolla tubes marks, in this respect, an advance over those plants 

 in which such blending does not exist. But it would be a 

 mistake to suppose that the flower of the cranberry is struc- 

 turally more complicated than the pea or the violet flower. 

 As in the case of the willows and the orchids just compared, 

 the cranberry belongs to one of the lowest orders of corolla- 

 tube-producing plants, while the peas and violets are relatively 

 high types of the generally lower series, in which no corolla 

 tubes are formed. 



With this explanation of a somewhat difficult point look- 

 ing toward an answer to the question, why is one flower con- 

 sidered of higher type than another? there may now be dis- 

 cussed the eight remaining orders of two-seed-leafed plants 

 in which corolla tubes rather than separate petals are almost 

 universally the rule. 



