2．Argumentation，即评论类型的文章。此类文章中，作者针对一个业已存在的主张提出自己的评价，不同意或不完全同意该主张，或者对已存在的主张做较大的补充，还要给出替代方案。评论的态度以反驳或攻击性的负评价较为多见；但是，正评价或正负评价都有的复杂态度也并不罕见。 

　　例文： 
Traditionally,　pollination　by　wind　has　been　viewed　as　a　reproductive　process　marked　by　random　events　in　which　the　vagaries　of　the　wind　are　compensated　for　by　the　generation　of　vast　quantities　of　pollen,　so　that　the　ultimate　production　of　new　seeds　is　assured　at　the　expense　of　producing　much　more　pollen　than　is　actually　used.　Because　the　potential　hazards　pollen　grains　are　subject　to　as　they　are　transported　over　long　distances　are　enormous,　wind-pollinated　plants　have,　in　the　view　above,　compensated　for　the　ensuing　loss　of　pollen　through　happenstance　by　virtue　of　producing　an　amount　of　pollen　that　is　one　to　three　orders　of　magnitude　greater　than　the　amount　produced　by　species　pollinated　by　insects. 
However,　a　number　of　features　that　are　characteristic　of　wind-pollinated　plants　reduce　pollen　waste.　For　example,　many　wind-pollinated　species　fail　to　release　pollen　when　wind　speeds　are　low　or　when　humid　conditions　prevail.　Recent　studies　suggest　another　way　in　which　species　compensate　for　the　inefficiency　of　wind　pollination.　These　studies　suggest　that　species　frequently　take　advantage　of　the　physics　of　pollen　motion　by　generating　specific　aerodynamic　environments　within　the　immediate　vicinity　of　their　female　reproductive　organs.　It　is　the　morphology　of　these　organs　that　dictates　the　pattern　of　airflow　disturbances　through　which　pollen　must　travel.　The　speed　and　direction　of　the　airflow　disturbances　can　combine　with　the　physical　properties　of　a　species’　pollen　to　produce　a　species-specific　pattern　of　pollen　collision　on　the　surfaces　of　female　reproductive　organs.　Provided　that　these　surfaces　are　strategically　located,　the　consequences　of　this　combination　can　significantly　increase　the　pollen-capture　efficiency　of　a　female　reproductive　organ. 
A　critical　question　that　remains　to　be　answered　is　whether　the　morphological　attributes　of　the　female　reproductive　organs　of　wind-pollinated　species　are　evolutionary　adaptations　to　wind　pollination　or　are　merely　fortuitous.　A　complete　resolution　of　the　question　is　as　yet　impossible　since　adaptation　must　be　evaluated　for　each　species　within　its　own　unique　functional　context.　However,　it　must　be　said　that,　while　evidence　of　such　evolutionary　adaptations　does　exist　in　some　species,　one　must　be　careful　about　attributing　morphology　to　adaptation.　For　example,　the　spiral　arrangement　of　scale-bract　complexes　on　ovule-bearing　pine　cones,　where　the　female　reproductive　organs　of　conifers　are　located,　is　important　to　the　production　of　airflow　patterns　that　spiral　over　the　cone’s　surfaces,　thereby　passing　airborne　pollen　from　one　scale　to　the　next.　However,　these　patterns　cannot　be　viewed　as　an　adaptation　to　wind　pollination　because　the　spiral　arrangement　occurs　in　a　number　of　non-wind-pollinated　plant　lineages　and　is　regarded　as　a　characteristic　of　vascular　plants,　of　which　conifers　are　only　one　kind,　as　a　whole.　Therefore,　the　spiral　arrangement　is　not　likely　to　be　the　result　of　a　direct　adaptation　to　wind　pollination. 

　　文章首段老观点讲风媒植物大造花粉弥补损失，第二段开始做了转折，不过作者并没有完全否定老观点，只是认为它很不全面，并且做了重大补充。 

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