108 CLIMAX FORMATIONS OF WESTERN NORTH AMERICA. 



akmmL Tte l irftirt feature of a society, that of a ccmtit^ within a contitJ, 

 oAen apiMnatitj pefttar than that of the cozi5ociati<Mi itself in the case ol 

 grMriand at iBttk, k doe to the difference in vegetation-forms and hence in 

 fi B ^liy i M l raqtanneBlB. A lodely may conceivably belong to the aaae 

 vesptetioo-lbim aa tiM conaociatkai or aaaociation in which it occiub, bat auch 

 eaaea are praelieaQjr voBkaamn, Apparent fnamplw! of thie hare all been 

 readily referred to soeeeaMonal eauaea, aa where a loraKapd area of Hardmm 

 pAaium occurs in praine, or one of AriaUda pw^ i uaa on the plama. The 

 abMMk iBtfaoabb rab IB that the aocaety belongs to a Tegetalk4anft of kmcr 

 r e quii eMenta than tiiat of the eonaodation. The forest will haive a oaetiea of 

 shnibe, herbs, mosees, etc., the chaparral of undershrubs, graaaes, and herfaa, 

 and the prairie of herba principally. In this connection, it is especiaQy 

 qtortant to * gM ttat aafannahe do not represent tree or shrub aocietiea 

 ingraadand,butareanineoMi i Je t ee]q piaMHo nof theDextstagema w 



The degree of control exerted by the society deariy depoidB upcn the M- 

 history rdations of the dominant and subdominant concerned. This is larigely 

 a matter of the heig^it and extent of the shoot, but the root alao i^ays a hatgt 

 part. In f OTeat the aodeties of varying rank, from dimb to moss or lidien, 

 are whoDy and obTkariy sobordmate to the trees. In chaparral this is abo 

 true to a kxge extent, but aodeties of miderahnibe and graases often play a 

 ii*iMipninw part. As to giiwiiiiil, the societies are frequently much mote 

 iiWM|a< lawin than the dnminant graasesy and at times thqr appear to be in 

 aonlroL In audi eaaea the conteol ia seasonaL EaA aoibdaninant reafdiea 

 a fM^T^Twitm in spring, aommer, or fall, when it seems to *V ''**^, hot tl 

 real rdations are '****'"^"*^ at the other seasons. This tendoicy of ""** to 

 appear daring a partiralar seaaon further eTplains the relation of daniaania 

 toaabdoasiaantB. Tliej not on^ & diliBRntdanandafaiyirirtae of their 

 ^FogBtaticMi-ionBa, bat these dBBMods are also made at fiflereut times. Soeie- 

 tiea eidubft a similar wnawisl rdation in forest and scrub, in which their time 

 of appearance ia afanoat wiioQy eontroOed by the dcaninanta.. In most 

 tiM rdatkm is so akfftang tiiat it is posdUe to dkstinggiBii two or more ; 

 daring a seaaon, nnribed by partienlar societies (Clwnentn, 1905 : 296 ; 1916 : 

 133). Vntu ti preeedmg (fiaeoasion, it is dear that varioas kinds hare 

 alnendy been <fistingaished (dements, 1916 : 132), and it is hi^^ probable 

 that adfl others win demand reeognition aa the study of vegetation beeomea 

 aore detailed and accorate. 



llie society is not a aabdnridon of the eonaodation in the aaane way that tfaia 

 is of the association. The latter condwtw of its conaoriitionB, gronped or 

 dn^; they oocopy its total area. The consociation does not rvmmi of 

 a nd rt ie a , bat the latter merely occur in it or throat it to a laiBer or 

 degree. Thia ia readily aeen to be doe to Jte hmrit dMferenee in 

 fonna and to the wMwrmal nature of snCiieti f a Aa a conseqaenoe, a 

 aoeiety may oceor not only in two or more (fifterent c o nanc ia ti nna , bat alao 

 in two or more aaBodatioos of the same formation, It may extend 

 leas eoaiiBtnonilly oiver wide Btretdiea, or it may recar aa aoeeesdi 

 or phydcal taatota d rtw inii i e A typical example of thia is i^Mra 

 whidi occurs in nearly every aaaodation and fonanciatinn of the y bmIbimI 

 wUe the chisely related aodety of P. sijajrifctlls is restricted to the 



lOBma aBMiar coBBBaimities of 



