







254 



DR. M. T. MASTERS ON THE MORPHOLOGY, 





radiate towards the centre, and sometimes the rows are separated 

 by medullary rays. The phloem-cells, on the other hand, are 

 much less regularly disposed. The total quantity of xylera and 

 phloem in relation to the pericycle and the relative amount of 

 xylem and phloem in the same bundle vary very considerably 

 in different species. 



A single unbranched bundle within one pericycle is met with 

 in Fitzroya, Juniperus, Cryptomeria, Sequoia, Athrotaxis, Cepha- 

 lotaxus, Taxus, Torreya, Ginkgo, Phyllocladus, Saxe-Goihea, Po- 

 docarpus, Cunninghamia, Araucaria, Sciadopitys, some species or 



monticola 



flexilis, refli 











Parryana, Balfouriana, aristata, Cembra, in Abies nobilis, magni- 

 fied* Keteleeria Fortunei, Pseudotsuga Douglasii, in species of 

 Cedrus, Picea, Larix, Tsuga, &c. 



A branched bundle occurs in the cladodes of Sciadopitys, in 

 Abies amabilis, grandis, Lowiana, concolor, lasiocarpa, Frasert, 



balsameay sibirica, 

 PindrowJVebb 



fi 



bifida 





Pinsapo, numidica &c, and in the following species of Pinus : 

 bract eata, religiosa, contorta, muricata, Fngelmanni, Coulter i, 

 ponder osa, Montezumce, Torreyana, Jeffrey i, Pinaster, Tceda, Sa- 





biniana, serotina, rigida f insignis, pungens, tuberculata, inops, 

 clausa, mitis, glabra, Banksiana, palustris, cubensis, Laricio, and 



silvestris. 



In considering these characters as available for systematic 

 purposes it may here be remarked that the arrangement of the 

 stomata usually affords a good (that is a relatively little variable) 

 character, that the presence and thickness of the hypoderm are less 

 reliable, being dependent on climatic influences and exposure, 

 that the characters afforded by the mesophyll are of great import- 

 ance, though not worked out in all the species, that the position of 

 the resin-canals is of more consequence than their number, while 

 the undivided or branched condition of the vascular bundle, as 

 pointed out bv Messrs. Coulter and Hose, in a character of high 





. .i 









value. M 



structural characters are, however, no more 



absolute than other diagnostic points, although serviceable " for 

 use in the absence of other characters" *. 







* In addition to the authors incidentally mentioned and to the general 

 treatises of Straaburger, Sachs, De Barv, Van Tieghem, &c., reference may here 









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