Embryo - which is derived from the zygote. The appearance of these structures vary with the species. As the names suggest, perhaps the major difference is that monocots have a single cotyledon vs. two in dicots. The germinating seed is initially heterotrophic - it subsists off of its own stored food reserves until it becomes photosynthetically competent. Thus, it must contain a nutrient source.
Seeds are an interesting hybrid of maternal and offspring tissue .
The seed coat is derived from the integuments of the ovule. The ovary develops into the fruit. Botanically, fruits are derived from the ovary or reproductive parts of the plants. Many foods that we call vegetables are actually fruits, and vice versa. Seeds vs. Fruits.