ECCENTRIC GROWTH. 287 



attained. Thus, in fig. 99, eccentric in the plane of sepal 2, 

 the increased rate of development of the posterior side of the 

 flower involves the ontogenetic origin of members numbered 

 according to their theoretical value to appear to the eye as if they 

 had been produced in the sequence 2, 5, 7, 4, 10, 1, 3, 8, 12, etc. 

 If, again, in the same figure, numbers 1-5 represent a normal 

 quincuneial calyx, and 6-10 five spirally arranged succeeding 

 petals, approximately alternating with them, 11-18 would be 

 eight stamens and 19-21 three carpels, all in normal spiral series. 

 Of these stamens, however, the apparently oldest would be 12, 13, 

 15 on the posterior side, 11, 18, and finally 14, 16, 17. 



It now becomes of interest to compare the interpretations put 

 forward to explain the construction of the flower of Tropaeolum 

 (Freyhold, Buchenau, Eichler, Van Tieghem, Eohrbach, Cela- 

 kovsky). The simple view which regards the androecium as 

 consisting of two whorls of five, and the flower as cyclic, but with 

 two median stamens suppressed (Van Tieghem, Eichler), affords 

 no suggestion whatever as to the peculiar irregular ontogeny of 

 the eight stamens. Nor can any attempt at manipulation of a 

 " I divergence," which would follow, according to Schimper 

 and Braun, from the presence of eight members, account for the 

 anomalous and yet fairly constant order of development, and 

 more particularly for the postero-lateral position of the first to 

 appear. Thus the sequence for a left-hand flower is : 



8 4 * 

 2 1 

 6 7 



3 5 



According to the excellent account and figures of Eohrbach.f 

 the position of 4, 5, 6 may vary somewhat. The calyx is ad- 

 mittedly spiral, but the axis is not apparently eccentric at this 

 stage ; the corolla is also spiral, as shown by Eohrbach ; the second 

 petal being distinctly larger than the others at first, shows that 

 eccentricity now sets in. The fact that the stamens arise singly 

 in an irregular order, and not strictly " ascending " or " descending," 

 implies that whorled symmetry is out of the question and that 



* Eichler, Blutheiidiagramme, ii. p. 298. t Bot. Zeit, 1869, p. 848. 



