594 K. J. HARVKY-GIBSON AND MINNIE BRADLEY ON 



The stem anatomy of other genera of Papaveracese may now be considered. 



Meconopsis cambrica, Vig. — The main axis is short and thick, and from it 

 numerous leaves and flower-stalks arise. The exodermis is indistinct, and the inner 

 chlorophyll-bearing layers are often sclerotic in varying degree. The endodermis is 

 indefinable, the pericycle, five or six layers deep, is sclerotic and merges gradually 

 into the non-sclerotic medullary rays in the interfascicular regions and abuts directly 

 on the hard bast opposite the bundles. The medulla is non-sclerotic and often 

 tistular. The bundles, which are of the normal dicotyledonous type, are arranged 

 in circles, and each is surrounded by one or two clearly denned layers of conjunctive 

 cells. The hard bast is strongly sclerotic, while the sieve tubes are prominent and 

 show sieve areas on the walls adjacent to the phloem parenchyma. These cells also 

 exhibit a tendency to bulge out and meet similar protuberances from neighbouring 

 cells, as do the laticiferous elements in Papaver. Latex tubes also occur and run 

 parallel with the phloem elements, but without any sign of branching. 



Argemone mexicana, L. — The exodermis in this species is fairly well denned, but 

 no endodermis can be distinguished. The protoxylem elements are scattered amongst 

 an inner mass of parenchyma which is itself bounded by a well-marked V-shaped 

 band of sclerenchyma. Laticiferous tissue occurs in the pericycle, in the conjunctive 

 tissue of the medullary rays, along the borders of the primary phloem and in the 

 secondary phloem, in the xylem parenchyma, and a few elements are found even in 

 the hard bast and in the lignified tissue bordering the inner parenchymatous mass 

 of each bundle. The elements are branched, and have sinuous walls in the phloem, 

 but in other regions resemble more in form the tissues among which they occur 

 (fig. 14). Prominent perforations occur on the walls of the latex tubes. The stem 

 anatomy of Argemone hispida and of Argemone ochroleuca differs in no essential 

 respect from that of Argemone mexieana. 



Chelidonium majus, L. — The exodermis of this species is fairly well defined, but 

 its cells more nearly resemble those of the epidermis than of the cortex, which 

 consists of a single layer of green cells (fig. 15). There is no obvious endodermis, 

 and the pericycle is represented by about six layers of sclerotic cells, the intensity 

 of sclerosis diminishing from without inwards, so that the pericycle gradually merges 

 into the non-sclerotic medullary rays. Laticiferous tissue occurs at the periphery 

 of the vascular bundles, more rarely in the secondary phloem and medullary rays. 

 Most of it consists of a series of cells placed end to end, showing no lateral branching, 

 but those cells which occur in the medullary rays are less regularly superposed and 

 occasionally show indications of branching. Their walls contrast with those of 

 Papaver in being free from perforations save, infrequently, where the lateral walls 

 are contiguous. 



Glaucium corniculatum, Curt. — The peripheral region is shown in fig. 16. 

 There is no definite endodermis, but just within the chlorophylliferous zone is a 

 region of sclerotic cells five to ten layers deep which comprises pericycle, hard 



