The principal conjugated acetylenic acids present in either the seed or somatic fats of seven species from the Olacaceae and Santalaceae families have been described in previous parts of this series. They display characteristic absorption spectra in the u.v. region. The spectra of the simpler polyenyne chromophores are now well established and have, for example, been tabulated by Bohlmann. Our previous work has consisted in isolating certain individual acids displaying these chromophores, and in determining the location and orientation of the chromophore in the molecule. It seemed desirable before further close examination of particular plant lipids to survey spectroscopically a larger number of plant lipids drawn from the Santalaceae and related families. If chromophores were present more unsaturated than those so far observed they would be readily detected. A survey could also disclose more convenient sources for the octadecadienediynoic acid, the isolation of which has been described, but for which the structural elucidation is incomplete; and for an enetriynoic acid of which traces had been found. Thirty-four species from five related families have been collected and extracts were prepared as soon as possible by the methods which have been adequately described in earlier communications. The root lipids of all species have been examined spectroscopically, but no corresponding examination has been made of the seed fats. This work terminated in 1960 and lacks the projected supporting detailed chemical examination. However, it seemed desirable to place the results on record, for they suggest some generalizations and concern some plants in which the content of conjugated acetylenic acids is high. Table 1 summarizes the information and includes apposite information from our earlier work. The compositions of the fats reported in Table 1 were not always obtained from direct spectroscopic examination. When the spectrum was too complex for direct analysis the fats were hydrolysed by cold ethanolic alkali and the component acids were partially separated by reverse-phase chromatography as described previously.