Fertilisation of Scrophularia aquatica and nodosa. 379 



The Injlorescence, Floi^al Structure, and Fertilisation of 

 Scrophularia aquatica and S. nodosa. By T. Wemyss 

 Fulton, M.B., CM. (Plate XIII.) 



(Read 14th January 1886.) 



The plants of the germs Scropliularia present many 

 points of interest in regard to their floral arrangements and 

 mode of fertilisation. In order fully to appreciate how the 

 one is related to the other, it is necessary to consider in 

 some detail both the whole inflorescence and the flower. 

 The inflorescence, which is of the indefinite kind, consists 

 of a tall raceme, sometimes over 7 feet high, bearing lateral 

 branches placed practically in alternating opposite pairs, each 

 of which forms a dichotomous or dichasial cyme, but it 

 may, from partial suppression of the later ramifications, 

 ultimately assume a helicoid type. Although the racemes 

 of both species have the same general character, they 

 exhibit some points of difference. In S. aquatica the 

 cymes are comparatively short, and nearly horizontal ; they 

 tend to be separated vertically by wide intervals, but have 

 their flowers brought approximately to the same horizontal 

 plane by a peculiar twisting of the secondary and succeeding 

 branches through a quarter of a circle — the members of 

 each pair in an opposite direction. The cymes of S. nodosa 

 are longer, directed obliquely upwards, less separated, and 

 their ramifications are not appreciably twisted. It is im- 

 portant to note that each cyme behaves, as it were, like a 

 distinct inflorescence, continuing to produce flowers of 

 successive generations, while the raceme is adding to the 

 number of cymes at the top. Consequently, while there 

 is a centripetal evolution of the flowers of any given 

 generation, yet flowers are always to be found scattered up 

 and down the stem, those of the first generation above 

 being contemporary with those of increasingly later genera- 

 tions below. A single raceme may produce several hundreds 

 of flowers in the course of a season, but comparatively few 

 exist at the same time, and the plants grow close together 

 in clumps, so that many racemes are brought into close 

 proximity. The importance of these facts will be seen 

 when we come to the mode of cross fertilisation. 



