INTRODUCTION. XXIX 



missing, and the flowers are therefore regularly unsymmetrical, a 

 character by which these orders may be constantly known, when 

 the form of their corolla will not distinguish them. In Phytolaccese 

 there is a constant tendency to a want of symmetry ; and this is one 

 of the characters by which that order is known from Chenopodeae. 



That part of the stamen which contains the fertilizing matter 

 or pollen is known by the name of the Anther, and is a case 

 usually consisting of two parallel or slightly diverging cells, con- 

 taining pollen, and opening by a longitudinal fissure ; but from this 

 plan many deviations take place, which are of great value in deter- 

 mining affinities. Thus, all Malvaceae, properly so called, and Epa- 

 cridese, have but one cell ; in Laurineae and Berberideae the valves 

 are hinged by their upper margin ; in Ericeae the pollen is emitted 

 by pores ; in Melastomaceae the same takes place, along with a 

 peculiar conformation of the lower part of the anther ; in Hamame- 

 lideae dehiscence is effected by the falling off of the face of the 

 anthers : but in Solaneae, the genera of which have usually their 

 anthers bursting longitudinally, the genus Solanum itself opens by 

 pores. — The mode in which the anther is united with the filament is 

 sometimes taken into account, as in Anonaceae, Nymphaeaceae, Hu- 

 miriaceae, and Aroideae, or Typhaceae, in which they are always 

 adnate ; and Gramineae, in which they are as regularly versatile. 

 But this modification appears of no great moment, nor indeed does 

 any peculiarity of the connectivum, all kinds of forms of which are 

 found in Labiatae ; and even in the small order of Penaeaceae we 

 have anthers with the connectivum excessively fleshy, and in the 

 ordinary state. 



Pollen rarely affords any marks by which affinities are to be 

 traced. The most remarkable deviations from it exist in Asclepiadeae 

 and Orchideae ; the former having it always in a state of concretion, 

 resembling wax, by which they are known from Apocyneae, and the 

 latter having it frequently so, but also containing numerous genera, 

 the pollen of which is scarcely distinguishable from its ordinary 

 powdery state. 



Immediately between the stamens and the ovarium is sometimes 

 found a fleshy ring or fleshy glands, called a Disk, and supposed for 

 very good reasons to represent an inner row of imperfectly developed 

 stamens. The presence of this disk is constant in Umbelliferae, 

 Compositae, Labiatae, Boragineae, Rosaceae, and many others, while 

 its absence is equally universal in others. It is not, however, much 

 used as a principal mark of distinction, its real value not having been 

 yet ascertained. There are some highly curious modifications of it 

 in Rhamneae and Meliaceac. It is a very remarkable fact, that in 

 Gentianeae and their allies, which have the pericarpial leaves right 



