258 ON THE CAULOTAXIS OF BRITISH FUMARIACE^. 



on the right, so that the inflorescence was what systematists term 

 leaf-opposed. At the second node there was a leaf on the rhjht, with 

 a lateral branch in its axil ; the axillary branch terminated in three 

 flowers, just below which was a leaf with an axillary branch of the 

 second order. At the third node the leaf was on the left, and opposite 

 to it was a peduncle bearing flowers. At ihefoxirth node there was 

 a leaf on the left, with an axillary branch. At WiQ fifth node the 

 leaf was on the right, and a leaf-opposed peduncle on the left. At 

 the sixth node there was a, leaf on the right, and from this point the 

 stem was continued into a peduncle with flowers, so that here the 

 peduncle was terminal. 



From this it appears that, in the specimen described, leaf and 

 axillary branch alternated regularly with leaf and opposed peduncle. 

 Many other specimens subsequently examined exhibited essentially 

 the same organisation, the inflorescences being invariably leaf- 

 opposed, except at the apex of the shoots, where they are terminal. 

 We may take it, therefore, that there is some reason for regarding 

 this as the typical arrangement of leaves, branches, and inflores- 

 cences, and they may represent it diagrammatically as 'in Fig. 1. 



Interpreting the arrangement on the same principles as were 

 applied to the Geraniums,* it will be obvious that the long slender 

 shoots of this plant are in reality pseiulaxes or sympodia, each one 

 being made up of a series of successive lateral branches, which 

 have become organised into a continuous axis. The leaf-opposed 

 peduncles are thus the terminal portions of each section of the 

 pseudaxis, which have become pushed aside by the more vigorous 

 growth of the lateral shoots. Hence a rational view of the whole 

 structure may be represented as in Fig. 2. 



For descriptive purposes it will be convenient in future to speak 

 of the sections of the pseudaxis as ^^ caulomeres,'' and to distinguish 

 the caulomeres as uninodal, binodal, &c., according to the number 

 of nodes they carry. Those with more than three nodes may be 

 termed multinodal. Using this language, the shoots of the speci- 

 mens referred to may be described as pseudaxes, built up of binodal 

 caulomeres. As stated, however, these were but the terminal 

 portions of the shoots, and it became necsssary therefore to see 

 whether the same structure obtained in the older parts. For this 

 purpose it was deemed best to have recourse to young plants, 

 whose growth and development could be watched from the earliest 

 stages until they reached maturity. The results, which are sum- 

 marised in the next paragraph, sliow that the formation of pseud- 

 axes, in the way described, in'actically prevails over the whole 

 plant, the chief point of diflerence being that in the older portions, 

 one, two, or a few of the caulomeres are of a higher order than the 

 binodal. 



In germination the hypocotyl elongates more or less, and raises 

 the cotyledons above the soil, where, as is usual among dicotyledons, 

 they present themselves as a pair of simple, entire, opposite leaves 

 (Fig. 3). The leaves subsequently developed appear in pairs, which 

 decussate regularly with one another, but the petioles of each pair 



* Loc. cit. 



