196 THE SCOTTISH BOTANICAL REVIEW 



united together, form an apparently entire envelope. This is 

 the concept of Rostowzew, which, however, has thus far to be 

 supplemented, that the " torsion of the capitulum " — if one 

 assumes such a thing — is not a subsequent event, but it 

 existed from the first ; in other words, it is " congenital." 

 Rostovv'zew does not mention that if this interpretation be 

 assumed, then the lateral capitula of the Ambrosia would 

 present one of the rare cases in which the " bracts " (Deck- 

 blatter) of lateral shoots have aborted completely. This 

 occurrence is known in the flowers of the cruciferze, etc., in 

 which one can correlate the abortion of the bracts with ex- 

 cessive crowding originally undergone by the flower-primordia 

 before the elongation of the axis of the inflorescence. In the 

 case of Ambrosia, this would be all the more striking because 

 the female inflorescences possess well-developed bracts, 

 although they are quite as closely crowded together as the 

 male ones. In no instance have I observed in the male 

 capitula even a trace of a subtending bract. 



The second possibility is that the first leaf (indicated by a 

 in fig. i) is the bract (Deckblatt) of the capitulum. The 

 manner in which {a) develops from the primordium that 

 gives rise to (a) and {b) is similar to what occurs frequently 

 in flowers and inflorescences. In this instance the bract, so 

 to speak, is late in being formed. It does not develop in 

 advance of its axillary shoot, but from a primordium common 

 to both. The thing that surprises one is that the axillary 

 shoot should arise on the under side of the bract, and not, as 

 usual, on the upper side. But, after all, this is no more 

 wonderful than the " congenital torsion " already referred to, 

 nor is it quite without precedent amongst other Dicotyledons. 

 The remarkable flowers of Erythrochiton hypophyllanthus 

 are situated on the under side of the leaf ; also the axillary 

 branches on the creeping shoots of some of the terrestrial 

 Utricularise arise on the side of the leaf furthest away from 

 the growing-point.^ 



In other respects it may be assumed that the position of 

 the male capitula of Ambrosia means the same thing as the 

 torsion (entirely brought about by their weight) of the male 

 inflorescences of Corylus, Almis, Juglans, or the torsion of 



^ K. Goebel, [/(ruttlarta {" Anna.1. du jardin botan. de Buitenzorg," vii. 1889). 



