io75 
Haustorium of Striga lutea. 
The fact that the haustoria here are clearly exogenous, and apparently 
organs sui generis , does not of course necessarily mean that in other parasitic 
plants they are never formed by the modification of root primordia, but it 
leads one to wish for more exact and detailed descriptions of their origin 
and development than are generally given, before coming to a conclusion 
on the point as regards any one plant. 
Summary. 
i. Striga lutea is a semi-parasitic South African annual which grows 
* as a root-parasite on native grasses and on the maize. It consists of 
a slender shoot, the underground portion of which bears many adventitious 
roots on which haustoria arise. 
3. These haustoria are markedly exogenous in origin, being formed by 
the division of cells of the subhypodermal or hypodermal layer of the root, 
which push up the overlaying layers to form a finger-like protuberance. 
3. When this meets the root of a maize plant, its epidermal cells grow 
out as papillae and bore their way into the host, by secreting a ferment 
which dissolves its tissues. 
4. Down the centre of the haustorium a line of tracheides is now 
formed, linking the vessels of root and parasite, and by division of the 
cells surrounding this axial strand a 4 nucleus ’ of parenchymatous cells is 
formed, which gives the haustorium a globular outline. 
5. The mode of nutrition of the parasite is obscure. There is free 
passage of water and salts from the host, but although the parasite passes 
a portion of its life-history underground as a total parasite, no system is 
formed for the conduction of assimilated food. 
6. The haustoria of this plant are exogenous in development, and are 
probably to be regarded as organs sui generis. 
Botanical Laboratory, 
South African College, 
April 24, 1912. 
Literature cited. 
1 . Barber, C. A. : The Haustorium of Santalum album. Mem. Dep. Ag. Ind., Bot. Ser., vol. i, 
1906. 
2 . Benson, Margaret : Root Parasitism in Exocarpus. Ann. Bot., vol. xxiv, 1910, pp. 667-77, 
PI. LV. 
3 . Cannon, W. A. : The Root Habits and Parasitism of Krameria canescens , Gray, in D. T. 
Macdougal and W. A. Cannon, On the Conditions of Parasitism in Plants. Carnegie 
Institution of Washington, Publication No. 129, 1910. 
4 . Davy, J. B. : Witchweed or Rooibloemetje. Trans. Agric. Journ., April, 1904. 
