Jacket - Any layer or tissue which is covering an archegonium, capsule, or sporogonium.

Jacket Cell - An outer cell which is usually of a reproductive organ.

Jamin's Chain Jaminian Chain - A series of short threads of water which are separated by bubbles of air, in the vess1es of plants.

Juvenile Form - A young plant having leaves and other features different from those of a nature plant of the same species.

Juvenile Leaf - The form of leaf found on a sporeling or seedling, when it is different markedly from the leaf of the adult plant.

Juvenile Stage - A special stage in the life-history of some algae from which the ordinary plant is developed as an outgrowth.

Juvenility - The condition expressed in immature organisms, which are generally smaller in size than the adults and lack reproductive capability. The seedling represents the juvenile stage of many plants. Juvenile leaves are different from mature leaves.