XXXll INTRODUCTION. 



of all Primulaceae capsular ; but Marcgraaviaceae, Melastomaceae, 

 Myrtacese, Ranunculacese, and Rosaceae, and a crowd of other 

 orders, contain both baccate and capsular, dehiscent and indehiscent 

 genera. 



The characters obtained from the position of the Seed are of the 

 same value as those from the position of the ovula ; in addition to 

 which, the peculiarities of the testa are made use of. In some 

 Monocotyledonous orders, as Asphodeleae and SmilacetB, the texture 

 is employed as a mark of distinction ; its being winged or otherwise 

 distinguishes Meliace* from Cedrelete, and the presence of a fungous 

 swelling about the hilum is a good characteristic of Polygalete. — 

 Linnean botanists make a distinction between naked and covered 

 seeds, attributing the former character to Labiatse, Boragineae, &.c. ; 

 but the sense in which they use the term is so manifestly erroneous, 

 that botanists were at one time led to believe that no such things as 

 naked seeds existed. It is now, however, known, from the accurate 

 observations of Mr. Brown, that certain tribes of plants do exist in 

 which the seeds are really naked, that is to say, susceptible of 

 impregnation and maturation without the intervention of any peri- 

 carpial covering. These are Coniferge and Cycadeae, orders exceed- 

 ingly remarkable in other respects, especially in the structure of their 

 vascular tissue. In consequence of these peculiarities, they have 

 been distinguished by A. Brongniart as a class of the same dignity 

 as Dicotyledons and Monocotyledons. Without assenting to this 

 proposition, to which I think there are great objections, it is impos- 

 sible to doubt that the naked seeds of these orders constitute a 

 secondary character of as much importance as any of which 

 botanists have knowledge. 



The substance which surrounds the embryo is called the 

 Alrumen, and its absence or presence constitutes a valuable 

 mark of distinction. There can be no doubt that when it exceeds 

 the bulk of the embryo very considerably, as in Ranunculaceae, 

 Papaveraceae, Umbelliferac, Grasses, and the like, it is of such 

 importance, that no plant destitute of albumen is likely to be found 

 appertaining to such orders ; but, on the other hand, I doubt very 

 much whether its presence or absence deserves much attention in 

 orders which are called by German botanists subalbuminous, — that 

 is to say, where the embryo and albumen are of nearly equal bulk ; 

 for it should be remembered, that it always exists in seeds at some 

 period of their existence, and that its remains may very well be 

 expected to be found in almost any seeds ; thus, in fact, both 

 albuminous and exalbuminous seeds are found in Proteaceac (Brown 

 in Linn. Trans. 10. 36); and even in Rosaccie, which are as free 

 from remains of albumen as any order, it is said to be distinctly 



