53 



REPORT OF THE CURATOR OF PLANT BREEDING 

 AND ECONOMIC PLANTS FOR 1924 



Dr. C. Stuart Gager, Director. 



Sir: I beg to submit herewith my report for the year ending 

 December 31, 1924. 



In addition to the investigational work on peas, hollyhocks, 

 and corn mentioned in the Reports on Research for 1924 (p. 43), 

 I have continued in charge of the "Ecological Section " — with its 

 various exhibits and demonstrations showing how plants are 

 fitted to cope with their environment. This section has attracted 

 many intelligent, inquiring visitors. Some of the exhibits have 

 made quite striking features, particularly the bed devoted to 

 flowering plants that live on other flowering plants. About 

 half the bed contains hemp plants with se\^eral hundred plants of 

 broom-rape (Orobanche sp.) growing and living on their roots. 

 These parasites have no green leaves and only their brown 

 flowering stalks with their light purple flowers appear above the 

 ground. i\s the roots of the hemp plants grow, new seedlings 

 of the Orobanche gain a foothold and send up their flowering 

 stalks, so that a continuous series of blooming broom-rapes is to 

 be had. The remainder of this bed is devoted to species of 

 dodder {Cuscuta) and their hosts. I have found Perillafriitescens 

 Britt. var. crispa Deane and the common garden balsam {Im- 

 patiens balsamina L.) excellent hosts for exhibiting the parasitic 

 nature of dodder, since both are ornamental, easy to grow and 

 both furnish the sort of food to make a fine growth of the dodder. 

 Dodder, being yellow, also shows ofif well, especially against 

 the purple-bronze leaves of Perilla. The yuccas and their silver- 

 winged, blacked-eyed Pronuba moths continued to be an inter- 

 esting and fascinating exhibit, especially to those with some 

 knowledge of the relation of this insect and plant. Another 

 feature of note was a peculiar grape, Viiis quadrangularis , from 

 Asia and i\frica that much resembles some of the cacti and 

 spurges, owing to its greatly reduced leaves. The absence or 

 reduction of leaf surface, of course, better fits it to cope with 

 arid climates. Much more could be accomplished with this 

 section if more and better trained gardening assistance could be 



