GOG R. J. HARVEY-GIBSON AND MINNIE BRADLEY ON 



(</) The intensity of sclerosis in the border of the internal parenchymatous 

 mass. In some forms the border is non-sclerotic, in others feebly so, 

 while in others still, e.g. Argemone mexicana and Bocconia microcarpa, 

 the sclerosis is intense. This feature is, however, not constant, for the 

 genus for Argemone hispida has no sclerotic border. 



(h) The nature of the secondary thickening in the tracheae and tracheids is 

 distinctive of Romneya trichocalyx. 



(i) The sectional outline of the stem and the degree of differentiation reached 

 in the cortex, ridged stems generally having subepidermal pads of 

 collenchyma. 



The stem bases in the Papav^racese also exhibit a very uniform anatomical 

 structure. In all types examined, save Corydalis capnoides and Eschscholzia 

 californica, the vascular bundles as they approach the base of the stem proceed to 

 unite into a cylinder broken only by the entry of the leaf-traces of the radical 

 leaves. The stems are not all equally lignified ; thus Bocconia microcarpa, 

 Romneya trichocalyx, and Papaver nudicaule have well-lignified stem bases, those 

 of P. Rhceas and many others are only moderately lignified, while those of 

 Chelidonium majus, Corydalis capnoides, and C. racemosa are scarcely woody at 

 all, their secondary xylem consisting almost entirely of unlignified parenchyma. 

 The secondary xylem consists of tracheae, tracheids, xylem fibres, and parenchyma. 

 In the woody stem bases the fibres predominate, while in the non-woody forms the 

 parenchyma is more abundant. The vessels and tracheids of the secondary xylem 

 are often pitted, but in many species of Papaver the reticulate type is more common, 

 as also in yieconopsis cambrica and Chelidonium majus. As a general rule reticulate 

 elements are more common in the secondary xylem of non-woody forms, but Papaver 

 alpinum and P. nudicaule are exceptional in this respect. 



The secondary phloem consists of cambiform cells amongst which the sieve tubes 

 and companion cells are difficult to locate. 



2. The methods of leaf-trace entry, as has been shown, are numerous. Often the 

 same species presents three or four different types. The most common type is that 

 exhibited by Papaver Rhosas, P. dubium, P. Isevigatum, P. lateritium, and 

 P. rupifragum. Another type of entry is that seen in P. pilosum, P. alpinum, 

 P. nudicaule, and P. somniferum, while P. glaucum and P. orientale show characters 

 common to both, but at the same time with peculiarities of their own. Meconopsis 

 is the only other genus examined showing marked similarity to P. Rhosas, but it 

 possesses no anterior strands, a feature exhibited by Argemone only. The leaf-trace 

 insertions of Glaucium and Dicentra closely resemble each other, while those of 

 Eschscholzia, Hypecoum, Romneya, and Corydalis form another group, the remaining 

 genera showing special features of their own. 



3. Similarly the vascular system found in the axillary axis varies. The bundles 



