INTRODUCTION. lxi 



one-fifth are sterile and petaloicl, in Galacinerc every other one, in Aqui- 

 larineee two-thirds, in Bignoniacerc tlie uppermost of 5 is rudimentary. — 

 A peculiarity of a similar nature is the want of symmetry which sometimes 

 exists between the petals or sepals, and stamens. Supposing the flower to 

 be formed without abortion of any kind, and by a regular alternation of 

 metamorphosis, as is usually the case, the petals will be always some mul- 

 tiple of the sepals, and the stamens of the petals ; and of course any irre- 

 gularity in this respect will destroy the supposed symmetry. This is often 

 a point of much importance to observe; for example, in Boraginese the 

 stamens are always equal to the segments of the corolla, and the flowers 

 of that order are consequently symmetrical ; in Labiatte, on the contrary; 

 one at least of the stamens is constantly missing, and the flowers are there- 

 fore regularly unsymmetrical, a character by which these orders may be 

 constantly known, when the form of their corolla will not distinguish them. 

 In Phytolaccece there is a constant tendency to a want of symmetry ; and 

 this is one of the characters by which that order is known from Che- 

 nopodeae. 



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, containing pollen, and opening 

 by a longitudinal fissure ; but from this plan many deviations take place, 

 wdiich are of great value in determining affinities. Thus, all Malvaceae, 

 properly so called, and Epacrideae, 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, Nymphaeaceoe, Humhiaceae, 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 powctery 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 inne'; 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 uni- 

 versal in others. It is not, however, much used as a principal mark of dis- 

 tinction, its real value not having been yet ascertained. There are some 

 highly curious modifications of it in Rhamneae and Meliaceae. It is a very 

 remarkable fact, that in Gentianeae and their allies, which have the peri- 



