THE ANATOMY OF THE STEM OF THE PAPAVERACE^E. 601 



as above stated, are frequent ; thus one leaf-trace examined showed no forking of the 

 median strand, but one of the lateral bundles fused with the median one and the leaf- 

 trace was continued down the stem as one large and one small bundle, the former 

 formed by fusion of the median strand with one of the lateral cords. Later on these 

 strands fused also. In another case the complete leaf-trace failed to enter by one 

 gap ; the median and one of the lateral bundles entered through the main gap, while 

 the other lateral bundle inserted itself between two axial bundles, with which it 

 ultimately fused. The compound bundle so formed then behaved like an ordinary 

 lateral leaf-trace bundle, fusing with one of the forks of the median leaf-trace. 



There are two chief types of leaf-trace insertion in Meconopsis cambrica. In 

 the upper leaves inserted just below the flowers the leaf-trace consists of three strands 

 uniting into one cord which enters the axis system by a gap in that system. In the 

 lower leaves the leaf-trace consists of several strands, united ultimately into one 

 median and two lateral cords. An axillary branch occurs in the axil of each of these 

 leaves, whose vascular system splits into two parts, each half inserting itself on either 

 side of the gap in the stem system. The median strand of the leaf-trace enters the 

 gap, followed by the lateral strands. The median trace splits, and each half fuses 

 with the adjacent lateral cord. These two strands fuse later into one, which merges 

 into the vascular ring of the axis. 



In Argemone mexicana two types of leaf-trace insertion are also found. In the 

 case of the upper leaves the leaf-trace consists of several bundles showing a tendency 

 to aggregate into three groups. These give off well-marked anterior strands which 

 turn through 180 degrees, thus making the leaf- trace take the form of a circle of 

 bundles. The vascular bundles of the stem separate opposite the leaf insertion, and 

 the leaf- trace throws its anterior strands right and left as it enters. Irregular 

 fusions occur, so that ultimately the number of bundles in the stem is scarcely 

 increased by the leaf-trace entry. In the case of the lower leaves three or five 

 circles of bundles are found. The median series enters first, while the lateral circles 

 follow, as shown in fig. 36. When an axillary branch is present some of its bundles 

 are sometimes intercalated between those of the leaf-trace, but usually all of it passes 

 down the stem, half on either side of the leaf-trace. 



The tendency for the leaf-trace bundles of the lower leaves to unite into three 

 or five circles is not so marked in A. hispida; the anterior strands are later in 

 appearing, and are not so well developed. The same features are presented by 

 A. ochroleuca. 



The leaf-traces in Chelidonium majus are multifascicular at their points of in- 

 sertion, and the vascular system of the axillary branch forms two semicircular cords, 

 the gaps left being opposite the main axis and the leaf-trace. The median strand of 

 the leaf-trace enters by the gap opposite to it. A gap is then formed in each of the 

 semicircular cords coming from the axillary branch, and the lateral strands of the 

 leaf-trace enter by these gaps. The whole of these bundles may maintain an 



