6 ROOT HABITS AND PARASITISM OF KRAMERIA CANESCENS. 



have been employed for a variety of uses, among" which may be mentioned 

 the adulteration of wines. Species of the genus have been cultivated at 

 Kew, but, so far as I have been able to learn, it is nowhere in cultivation 

 at present, at least in Europe.* 



Three species of Krameria have been reported from southern Arizona, 

 of which K. canescens and K. parvifolia are known to be root-parasites. 

 The third species, which is not found on the domain of the Desert Labo- 

 ratory, has not been studied in this connection. 



Krameria parvifolia was found on Parkinsonia micropay Ha only, although 

 some search was made to determine its relationship with other possible 

 hosts. Krameria canescens was seen on a variety of hosts, for which reason 

 the present account of the parasitism of the genus is confined to observa- 

 tions on this species. 



The following are the hosts of Krameria canescens, as determined to the 

 present time: Acacia constricta, Covillea tridentata, Encelia farinosa, Ephe- 

 dra antisypliilitica, Franseria dumosa, Lycium andersonii, Menodora scadra, 

 Parkinsonia aculeata, Parkinsonia microphylla, Prosopis velutina, and Zizy- 

 pli us parry i. A few instances of autoparasitism were noticed, and para- 

 sitism on Parkinsonia aculeata was induced in cultures. 



Krameria canescens is a sparingly-branched shrub, gray in color. During 

 the most of the year it is leafless, and the chlorophyll-containing shoots 

 assume the leaf -functions, but leaves reappear with the advent of the sum- 

 mer rainy season. 



Unlike most desert shrubs, Krameria has no recognized habitat pref- 

 erence, although it is mainly to be found on the slopes where its favorite 

 host, Covillea tridentata, is most abundant. This characteristic and the 

 added one (given in detail below) that its roots are placed close to the 

 surface, whether the soil is deep or shallow, are the only patent characters 

 which would, lead one to separate the species from the autotrophic ones as 

 being in any way odd or unusual. 



ROOT-SYSTEM OF KRAMERIA CANESCENS. 



The general root-habit of Krameria canescens may, perhaps, best be pre- 

 sented by describing the roots of a typical plant, such as that shown in 

 plate 1. The habitat of the plant is the flat west of the wash which sep- 

 arates Tumamoc Hill, on which the Desert Laboratory is situated, and the 

 eastern ends of the bajada which stretches eastward from the base of the 



*Through the kindness of the Director of the Royal Botanical Garden, Kew, I have 

 learned that Krameria triandra was cultivated in the Chelsea garden in 1830, and that 

 K. pauciflora was introduced into cultivation in Great Britain in 1824. No species of 

 the genus are at present in cultivation at Kew. 



The Director of the Konigliche Botanischen Garten in Dahlem writes that Kra- 

 meria is not in the houses of the garden, and adds, as pointing to its rarity, that although 

 the genus is well known for the tanning ingredients it may perhaps never have been in 

 cultivation in European botanical gardens. 



