SUPPRESSION OR ABORTION. 271 



being therefore placed in unlike conditions in such cases, so as to 

 favor the growth of some of them, and to arrest or restrain others, 

 either by pressure or by the abstraction of nourishment. Compare 

 in this respect the more or less irregular corolla of Scrophularia- 

 ceous plants (see the figures under Ord. Scrophulariacese) with 

 their stamens. The Mullein (Verbascum) is one of the few gen- 

 era of that family which has as many stamens as there are pet- 

 als in the composition of its corolla, and sepals in its calyx : but 

 even here they are unequal, and the posterior ones usually bear 

 imperfect or deformed anthers. In other instances, where the five 

 stamens are all present, indeed, the posterior one is either changed 

 into a bearded sterile filament, as in Pentstemon and Chelone, or 

 reduced to a mere rudiment, as in some Snapdragons ; or to a 

 deformed filament adherent to the corolla, and bearing a scale-like 

 body in place of the anther, as in Scrophularia. The four remain- 

 ing perfect stamens, in these cases, and nearly throughout the 

 order, are unequally developed ; two of them being longer than 

 the remaining pair ; as in Chelone, above cited, in .Gerardia, &c. : 

 the same thing is observed in most plants of the related orders 

 Acanthaceee, Bignoniaceae, Orobanchacea3, Verbenacese, and La- 

 biatae (which see). In such cases, viz., where of four two are 

 long and two are shorter, the stamens are said to be didynamous. 

 Not unfrequently, a further suppression takes place, and the two 

 shorter of these stamens either entirely disappear ; as in the Sage, 

 Monarda, Lycopus Virginicus, &c., among Labiates, and Gratiola 

 Virginica, &c., among the Scrophulariacese ; or else are reduced 

 to mere sterile filaments, such as those which may commonly be 

 observed in Gratiola aurea, in the Wild Pennyroyal (Hedeoma), 

 and in many other Labiate plants. 



482. The obliteration of one or more members of the corolla 

 follows the same laws. The loss of a petal from the circle is a 

 case of irregularity from unequal growth carried to the greatest 

 possible extent, or an arrest of the development of an organ from 

 an early period, and we may sometimes trace the gradation in re- 

 lated plants from the diminution or dwarfing of certain organs to 

 their total suppression. Thus, the papilionaceous corolla (468) of 

 Erythrina herbacea has its five petals, but four of them (all except 

 the posterior or vexillum) are small and inconspicuous : in Amor- 

 pha (Fig. 323), these same four disappear altogether, and the pa- 

 pilionaceous corolla is reduced to its vexillum alone. In some 



