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DR. M. T. MASTERS ON THE MORPHOLOGY, 



































the cortical and the central cellular tissue, and is usually undivided 

 for its whole length, breaking up only at the point of emergence 

 of the cotyledons to send branches to those organs. In Arau- 

 caria the vascular cylinder of the root is unbroken ; but in the 

 fleshy tap-shaped caulicle it divides into four wedge-shaped 

 masses with the xylem pointing towards the central pith. A 

 section made at the point of emergence of the cotyledons shows 

 four median bundles at right angles to the cotyledons. Above 

 the cotyledons the bundles are increased to six disposed in a 

 circle, while higher still they form a continuous cylinder. The 

 parenchyma of the ground-tissue in the caulicle is crowded with 

 starch-grains of different sizes ; and between the cortex and the 

 vascular ring it is traversed by a number of resin-canals disposed 

 in a circle, or rather ellipse, around the vascular ring ; another 

 circle of resin-canals lies just beneath the cortex. 



In a species of Cupressm with rather thick cotyledons, the 

 structure comprised one layer of brick-shaped epidermal cells, 

 but no hypoderm. Beneath the epidermis on the upper surface 

 only a single layer of palisade-cells was seen densely filled with 

 chlorophyll. The ceutral tissue consisted of loose parenchyma 

 with spheroidal cells, for the most part destitute of chlorophyll. 

 The central fibro-vascular bundle was, in section, transversely 

 oblong, with a well-marked endoderm enclosing the xylem and 

 the phloem, the latter directed, as in perfect leaves, towards the 

 lower surface, the xylem in the opposite direction. In Pinus 

 canariensis the three-sided cotyledons have a papular epithelium, 

 no hypoderm, a mesophyll of sphseroid or polygonal cells of uni- 

 form character, but differing in size, the inner ones being the 

 largest. There is a single fibro-vascular bundle surrounded by 

 an imperfectly developed endoderm. The structure of the coty- 

 ledon of P. Pinea is essentially the same. The peculiarities seem 

 to reside in the papular epidermis (epithelium), the absence or 

 imperfect development of hypoderm, and the absence of the 

 sinuous cells which are so marked a feature of the mesophyll of 

 the perfect leaves of the true Pines. 



Lestiboudois, in his ' Phyllotaxie Anatomique,' points out the 

 frequent want of concordance between th9 number of the 

 vascular bundles of the tigellum and the number of the coty- 

 led 



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4 



ons. 



Although there are numerous variations, the nor 







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position of the bundles is in the intervals between the cotvledons. 



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