ON THE CAULOTAXIS OF BEITISH FUMAKIACEiE. 259 



are not inserted at the same level. The interval between them is 

 scarcely perceptible at the base of the stem, but becomes consider- 

 able at higher levels, where the opposite and decussate phyllotaxis 

 becomes changed into an alternate one (Fig. 4). This, it may be 

 noted in passing, appears to be brought about by the elevation of 

 one of the leaves of each pair, through unequal growth on opposite 

 sides of the stem. The number of nodes between the cotyledons 

 and the first inflorescence varies in different seedlings, but is 

 generally an even number — four, six, or eight. In a few cases it 

 appears to be odd, and may actually be so ; but this only occurs, so 

 far as observation has gone, when the phyllotaxis at the first node 

 above the cotyledons is strictly opposite. In either case the first 

 caulomere is multinodal. After the first two or three, however, 

 the caulomeres usually become binodal, and so remain throughout 

 the whole length of the pseudaxis, except in some instances, where 

 they change again near the apex and become uninodal. Thus, as 

 a rule, each adds two leaves and two internodes to the principal 

 axis, and then runs out into an inflorescence. The lower leaf of 

 each often produces an axillary branch, whose organisation agrees 

 with that of the principal axis, except that the basal caulomere is 

 not of the same order in all cases. As intimated above, therefore, 

 the whole plant is built up of a series of pseudaxes, one of which 

 constitutes the main axis, while the rest form the so-called lateral 

 branches. Moreover, the caulomeres are for the most part binodal, 

 only the basal ones being of a higher order and the apical ones of a 

 lower. 



The other species of Corydalis included in British Floras, viz., 

 C. solida and C. lutea, are not regarded as true natives, though they 

 are occasionally met with. No opportunity of studying their 

 development has presented itself, but an examination of herbarium 

 specimens is instructive. In C. solida the stem is usually simple, 

 consisting of but a single multinodal caulomere, which terminates 

 in a racemose inflorescence. Here, then, the organisation of the 

 axis is reduced to its simplest form, and corresponds to that of the 

 basal caulomere of C. claviculata. In C. lutea the stem is more or 

 less branched, but both principal and subordinate shoots are 

 pseudaxes, built up of caulomeres, which, except at the base and 

 the apex, are generally binodal. 



Turning now to Fumaria, the other genus of the order, we find 

 a caulotaxis in general agreement with that of Corydalis, though 

 presenting minor modifications. Complete specimens of F. offici- 

 nalis show that the phyllotaxis is at first opposite and decussate, 

 but quickly becomes tetrastichous. Between the foliaceous cotyle- 

 dons and the first inflorescence eight leaves are often met with, 

 though there is some variety in this respect. Thus, the first caulo- 

 mere is of a high order, but the rest are for the most part binodal, 

 except at the apex, where they may become uninodal. Fumaria 

 capreolata is in close agreement with F. ojlicinalis. The only point 

 that need be referred to is, that here the leaves display a greater 

 tendency to produce two buds in their axils, instead of one. When 

 this occurs at a node which carries a leaf-opposed inflorescence, it 



