ArtiFiCiAl FlowErs ArE usED For sCiEntiFiC As wEll As For DECorAtivE purposEs. thEy ArE mADE From{{u}} (51) {{/u}}oF mAtEriAls, suCh As wAx AnD glAss, so skillFully thAt thEy CAn sCArCEly BE{{u}} (52) {{/u}}From nAturAl FlowErs. in mAking suCh moDEls, pAinstAking skill AnD Artistry ArE CAllED For,{{u}} (53) {{/u}}thorough knowlEDgE oF plAnt struCturE. thE{{u}} (54) {{/u}}oF glAss FlowErs in thEBotAniCAl musEum oF hArvArD univErsity is thE most FAmous in northAmEriCA AnD is wiDEly known{{u}} (55) {{/u}}thE sCiEntiFiC worlD{{u}}. (56) {{/u}}, thErE ArE sEvErAl thousAnD moDEls in ColorED glAss, thE work oF two Artist nAturAlists, lEopolDBlAlsChkA AnD his son ruDolph. thE intEntion wAs to hAvE thE CollECtion{{u}} (57) {{/u}}At lEAst onE mEmBEr oF EACh FlowEr FAmily nAtivE to thE unitED stAtEs.{{u}} (58) {{/u}}it wAs nEvEr ComplEtED, it ContAins morE thAn sEvEn hunDrED spECiEs rEprEsEnting 164 FAmiliEs oF FlowEring plAnts.{{u}} (59) {{/u}}DEtAil oF thEsE is ACCurAtEly rEproDuCED in Color AnD struCturE. thE moDEls ArE{{u}} (60) {{/u}}n loCkED CAsEs As thEy ArE too vAluABlE AnD FrAgilE For ClAssroom usE.

A．A vAriEty
B．somE
C．A sort
D．sEvErAl