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ANATOMY, AND LIFE-HISTORY OF THE CONIFERS. 



237 



Sequoia 



gigantea 4-5. 

 Tsuga 



canadensis 4. 



It is possible that an increased number of cotyledons might, 

 under certain circumstances, be advantageous by securing a 

 larger surface and a better chance in the competition with 

 neighbouring herbage. 



,tlv in different 







ine size ot the cotyledons also varies greatly 

 species. In Finns Pinea, for instance, they are 2 inches long 

 and proportionately stout; while in P. canariensts they are 

 equally long, but slender. The relative length of the cotyledons 

 and of the primordial leaves which follow them may afford diag- 

 nostic characters ; thus, in some species of Abies, Pinus, Larix, 

 Cedrus, and Athrotaxis the cotyledons are longer than the prim- 

 ordial leaves, while in some species of Thuya, Cupressus, &c. the 

 cotyledons are of about the same length as the succeeding leaves. 



In form the cotyledons are usually linear or linear-oblong, 



Retinospora (i. e. Thuya) obtusa, pisifera, 



Thuya^jiganlea. They are flat or 

 rounded on both surfaces. In some cases the midrib is not pro- 

 mment : in others, as in Abies VeitchiL sachalinensis. balsamea, 



Cryptomeria^„Zobbi, and 















cephalonica, and Apollinis, the 

 surface. In many of the species of Pinus the cotyledons are 

 3-sided, one side beiug anterior or inferior, the other two lateral 

 as regards the axis. The margins are usually entire ; but they 

 may be hairy, and in Pinus Strobus they are distinctly toothed 

 at the margins. Sometimes they are acute, or even mucronate at 

 the apex, as in many species of Pinus-, while in Abies they are 

 sometimes obtuse and even emarginate, as in Abies balsamea, 

 *ibirica, and Webbiana. In Picea excelsa they are thickened 

 at the base, and thus afford indications of the peculiar " pul- 

 vini " that are so characteristic of the adult branches in that 

 genus. 



Anatomy. — A few incidental remarks may here be given, with 

 a view to call attention to the importance of the subject in its 

 relation to physiology, and, as will be more fully exemplified in 

 the case of the lanv^s. to +h* investigation of natural affinities. 







caulicle forms 







JOTTBN. — BOTANY, VOL. XXYII 



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