Carbon nanotubes (CNTs) are grown vertically aligned on Fe catalytic particles deposited on a silicon oxide substrate at temperatures ranging from 550 to 950 degreesC by thermal chemical vapor deposition of acetylene. All CNTs have a bamboolike structure in which the curvature of compartment layers is directed toward the tip, irrespective to the growth temperature. Most of tips are closed and free from the encapsulation of Fe particle. However, the CNTs grown at 550 degreesC sometimes encapsulate the Fe particle at the closed tip. On the basis of experimental results, we provide a detailed growth model for the bamboolike structured CNTs grown using thermal chemical vapor deposition.