410 ANNUAL REPOET SMITHSONIAN INSTITUTION, 19 30 



having its flowers in a spike (as a flowering head), while the flower 

 head of the latter is a flat or saucer-shaped disk. The calj'x of 

 Pholisma is smooth, whereas that of Ammobroiiia is quite hairy and 

 the two parasites appear to have different host plants. 



Ammobroma is found in the sand dunes between Imperial Valley, 

 Calif., and Yuma, Ariz., and although fairly numerous in spots, 

 appeared not to be widely distributed, even though much apparently 

 suitable territory was explored. Our first examination of this plant 

 was on April 1, 1928, following a wet winter, and thereafter visits 

 to the locality were made at frequent intervals up to July 31, 1929. 

 The plant was found growing in almost pure sand of a pale buffy 

 color, and in the case of the best specimens the roots were found to be 

 in moist sand. Where the sand was dry at the point of contact with 

 the host root the stalks of the parasite were flabby and wilted. They 

 were found more abundant and in better condition in the depressions 

 between the sand dunes or at other points where it was evident that 

 more moisture was available. 



The flower heads were flat on the ground, and their similarity in 

 color to the sand caused them to be easily overlooked by a casual 

 observer. There were usually four to eight heads from a single con- 

 tact on the host root. These heads frequently appear on the surface 

 several feet from the host plant, but they are sometimes closer and 

 occasionally even partially under the branches of the host. 



Ammobroma was not reported from California until recently al- 

 though it was collected in Sonora, Mexico, in 1854 by Col. A. B. 

 Gray and again either in Arizona or in Lower California, Mexico, in 

 1858 by Carl Schuchard. In May, 1903, T. S. Brandegee reported 

 Ammobroma from California (collected by Alfred Stockton near the 

 Colorado River). 



It was reported again in April, 1925, by W. L. Jepson from the 

 Colorado desert in California (Ogilby near Hedges Mine). 



Through the interest of Mr. D. S. Hunt (known locally as " Peg- 

 leg "), this rare plant, growing in the sand dunes of Imperial County, 

 Calif., was brought to the attention of Dr. O. F. Cook a few years 

 ago, and in March, 1928, was shown to Mr. Carl S. Scofield. Mr. 

 Scofield collected specimens of young flowering heads and showed 

 them to Dr. Walter T. Swingle at the United States Date Garden, 

 Indio, Calif., in the latter part of March, 1928. Doctor Swingle de- 

 tailed us to make a thorough study of the plant and in particular to 

 ascertain its host plant. 



Before maturity, the heads are like a flat disk with a slight depres- 

 sion in the center, but as they grow older the top becomes more 

 convex, or saucer shaped, and some even approach a funnel shape. 

 When young, the disk appears entire, but may later form folds, or 

 lobes, and in some cases may even split into several parts, radiating 



