( ( When ( ( ( a ( plant 's ) ) ( vascular tissue ) ) ( develops ( as ( a ( central cylinder ) ) ) ) ) ) ( , ( it ( ( is ( said ( to ( have ( a siphonostele ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NP (DT a) (NN plant) (POS 's)) (NN vascular) (NN tissue)) (VP (VBZ develops) (PP (IN as) (NP (DT a) (JJ central) (NN cylinder)))))) (, ,) (NP (PRP it)) (VP (VBZ is) (VP (VBN said) (S (VP (TO to) (VP (VB have) (NP (DT a) (NN siphonostele))))))) (. .)))
When a plant's vascular tissue develops as a central cylinder, it is said to have a siphonostele.
(ROOT (S (NP (NP (JJ Present-day) (NNS plants)) (SBAR (WHNP (WDT that)) (S (VP (VBP have) (NP (DT a) (JJ complex) (NN vascular) (NN tissue) (NN system)))))) (VP (VBP are) (VP (VBN called) (NP (NN vasuluar) (NNS plants)))) (. .)))