The present invention relates to an agricultural machine (1) for the harvesting of plants. The machine (1) comprises a cutting mechanism (13), including cutting elements (see 14, 14&rsquo, figure 2), a conditioning device (18), including contra-rotating conditioning elements (see 19, 20, figure 4) and a transmission mechanism (27) to drive the cutting (see 14, 14&rsquo, figure 2) and conditioning (see 19, 20, figure 4) elements. The transmission mechanism includes a primary box (see 29, figure 7) and a secondary box (see 61, figure 7), each having respective casings (see 30, 64, figure 7) defining an inner volume. The primary box (see 29, figure 7) has a first input shaft (see 38, figure 7) driven by an external power source, such as the power take-off of a towing tractor, a first output (see 52, figure 5) driving the cutting mechanism, a second output (see 56, figure 4) driving the first conditioning element (19), and a third output which drives an input (see 66, figure 7) of the secondary box (see 61, figure 7). The secondary box further includes an output driving the second conditioning element (see 20, figure 4). A lubrication device (see 76, figure 4) is further provided which comprises a pump (see 77, figure 4), fluid lubricant and primary and secondary distribution systems. The pump (see 77, figure 4) and primary and secondary distribution systems are in fluid communication, such that the primary box (see 29, figure 7) and secondary box (see 61, figure 7) share fluid lubricant.
