( ( ( ( ( ( The ectoderm ) ( of ( basal disc ) ) ) ( is ( glandular ( which ( helps ( in ( ( fixing ( the Hydra ) ) ( with ( the substratum ) ) ) ) ) ) ) ) ) ; ) ( ( its ( central part ) ) ( can ( produce ( ( gas bubble ) ( which ( helps ( in floating ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (DT The) (NN ectoderm)) (PP (IN of) (NP (JJ basal) (NN disc)))) (VP (VBZ is) (NP (NP (NN glandular)) (SBAR (WHNP (WDT which)) (S (VP (VBZ helps) (PP (IN in) (S (VP (VBG fixing) (NP (DT the) (NNP Hydra)) (PP (IN with) (NP (DT the) (NN substratum)))))))))))) (: ;) (S (NP (PRP$ its) (JJ central) (NN part)) (VP (MD can) (VP (VB produce) (NP (NP (NN gas) (NN bubble)) (SBAR (WHNP (WDT which)) (S (VP (VBZ helps) (PP (IN in) (NP (VBG floating)))))))))) (. .)))
The ectoderm of basal disc is glandular which helps in fixing the Hydra with the substratum; its central part can produce gas bubble which helps in floating.
(ROOT (S (NP (NNP Gas) (NN bubble) (NNS holes)) (VP (VBZ helps) (NP (NP (JJ pumice) (NN float)) (PP (IN in) (NP (NN water))))) (. .)))