In this paper, we investigate the growth mechanism and dynamic behavior of in-plane solid-liquid-solid ͑IPSLS͒ silicon nanowires ͑SiNWs͒, mediated by indium drops which transform hydrogenated amorphous silicon into crystalline SiNWs. Two distinctive growth modes of the SiNWs have been identified: ͑1͒ the grounded-growth ͑GG͒ mode in which the produced SiNWs are fixed to the substrate and ͑2͒ the suspendedgrowth ͑SG͒ mode where the SiNWs are carried by and move together with the catalyst drops. A comparative study of the SiNWs produced in SG and GG modes provides important insights into the IPSLS mechanism and reveals the unique growth balance condition in the moving SiNWs/catalyst drop system. For the GG-SiNWs, the interplay between the front absorption interface and the rear deposition interface of the catalyst drop leads to an interesting growth dynamics, which can be described by a kinetic equation model. For the SG-SiNWs, direct evidences of the rolling-forward behavior of the liquid catalyst drop have been witnessed.