The disappearance t>f cell walls during the* cell fusion process in the plant was studied electron microscopically on the following objects. Hordeum vulgare: Differentiation in the central vessel of the root. Achras sapota: Origin of laticifers in the shoot apex. Phycomyces blakesleeanus and Hansenula wingei: Zygote formation. In the central vessel of Hordeum the end wall first swells, it is then detached in its entirety from the lateral wall, after which the breakdown process is completed. In Achras, Phycomyces and Hansenula cell wall breakdown during the cell fusion process takes place gradually, beginning in the centre. Enzymes that are in close contact with the plasma membrane probably play a part in this process. Both the skeleton which consists of microfibrils and the matrix of the cell walls are dissolved enzymatically. A cellulolytic enzyme is demonstrated in the root extract of Hordeum, a chitinolytic enzyme in the zygote extract of Phycomyces.