Commensalism Common Bean Seed Communities Companion Cells Companion cells always exist together with sieve-tube members . Sieve-tube members and companion cells are called sister cells because they originate from the same procambial cell or fusiform initial in the vascular cambium . The order of development is that the meristem cell begins to differentiate by dividing once to form two cells, then one of the two cells differentiates further into a companion cell and the other into a sieve-tube member. A compound leaf can be of two types, either pinnately compound or palmately compound . Thus, the leaf is compound if there are NO buds in the axils of the leaflets.
Compound leaves have their leaflets all oriented in the same plane.
Simple leaves, by comparison, have all their leaflets oriented in different planes. Compound leaves, when they fall from a tree, fall as a unit with all their leaflets in tact. Simple leaves, by comparison, fall separately. Thus, if there are fallen leaves on the ground that contain several leaflets, then the leaves are compound. Cone A cone is the reproductive fruiting structure of many tracheophytes.