The Endophytic System of Arceuthobium minutissimum, the Indian Dwarf Mistletoe

The Indian dwarf mistletoe, Arceuthobium minutissimum Hook f.is the most diminutive dicotyledonous stem parasite on Pinusexcelsa. The endophytic system is well developed, having a largenumber of anastomosing strands in the cortex and sinkers penetratingthe medullary rays in wood. The cortical strand is protostelicwith the central tracheary elements, the vessels, surroundedby paren-chymatous cells. An earlier report of absence of vesselsseems to be erroneous. The growth of the cortical strands iseffected by an apical cell. The sinkers typically associatedwith the rays of host, are composed of parenchymatous cellsand tracheary elements including vessels. They make contactswith the cells of the ray through pits present in the trachearyelements. The sinkers cause hypertrophy and even fusion of twoor more rays to form a composite medullary ray. The tracheidsof the host tissue also become stunted and contorted in shape.These observations are in agreement with those of other investigatorson American host species for Arceuthobium.