468 DR. M. T. MASTERS ON THE SUPERPOSED 



and in many Sapindaceae probably, in some cases certainly, owe 

 their origin to enation. The female flower of Sedum Bhodiola 

 has a formula as follows 



S 



P 



x 

 O, 



from which it might be inferred that the scales x were represen- 

 tatives of an outer row of stamens, the second row (antipetalous) 

 being supposed to be abortive. An examination of the flower m 

 a young state shows, however, that the scale is a mere outgrowth 

 or enation ; for in the unopened bud it is very small, but increases 

 rapidly as the flower opens, and serves as a honey-secreting 



Assuming, by way of illustration, that the petals of Primroses 

 and of Plumbaginacese are formed as outgrowths from the sta- 

 mens, they would afford illustrations of the process of enation, as 

 do also the corona of Passion-flowers, the outgrowths from the 

 surface of petals in various Caryophyllacese and Sapindaceae, the 

 appendages to the anthers in Asclepiadacese, &c. These out- 

 growths may occasionally assume the form of stamens ; but, 

 for all that, their mode of production may still be by enation rather 

 than by independent formation. In a particular form of Datura, 

 figured in my ' Vegetable Teratology,' p. 450, the arrangement of 

 the parts was as follows 



S5 



P5 

 X5 



P5 



St 5 



Here the inner row of petals may have been formed by chonsis, 

 while the petaloid outgrowths x were the products of enation from 

 the outer surface of the inner petals, similar to those sometimes 

 met with on the under surface of leaves. 



4. Abortion. — Superposition is perhaps most frequently brougn 

 about by abortion or suppression of intermediate whorls. Ih is l 

 obvious in the case of Vitis, where the stamens are superposed to 

 the petals, a second and outer row of antisepalous stamens being 

 represented by five glands of the disk, as shown by the formula 



