182 Transactions. — Botany. 



Art. XXIV. — On the Naturalized Dodders and Broom-rapes of 



New Zealand. 



By T. Kirk. 



[Read before the Wellington Philosophical Society, 6th July, 1887.] 



While the subjects of this paper are of exceptional interest to 

 the botanist, as parasitic flowering-plants which obtain the whole 

 of their nourishment from the unfortunate plants which they 

 use as hosts, they are often the cause of serious injury to the 

 farmer, who may find himself compelled to witness the destruc- 

 tion of his crops of lucerne, clover, and flax at tbe period when 

 he is expecting to reap his richest profits. It is chiefly from 

 this economic point of view that it is intended to regard them 

 in this paper. 



The seed of the dodder germinates in the ground, and de- 

 velopes a reddish or purplish thread-like stem, destitute of leaves 

 in all stages of its growth ; when the stem comes in contact 

 with a suitable host-plant, it developes minute suckers, which 

 may be termed root-suckers, as they enable it to grasp the plant 

 so firmly that it is impossible to detach it without killing both 

 host and parasite. When suckers are developed the true root 

 dies, having served its purpose ; thread-like stems are produced 

 with amazing rapidity, so that the host often appears to carry 

 masses of threads ; each short stem developes new suckers, and 

 adjacent plants are speedily involved. If left unchecked the pest 

 will soon destroy the entire crop, as its myriads of root- suckers 

 rapidly extract the greater portion of the assimilated nutriment 

 of the bost, which gradually becomes impoverished and dies. 



After a longer or shorter period, flowers are produced, some- 

 times in vast profusion. They are developed in small, globose 

 fascicles, and give ratber a pretty appearance to the unfortunate 

 hosts. Tbe corolla is entire, consisting of five petals, alternat- 

 ing with five stamens. At the base of each stamen is a curious 

 scale, which may be lacerated or fringed, or ciliated, and which 

 affords a useful means of distinguishing the species. 



Dodders belong to the Convolvulacetr, but differ from their 

 congeners in being destitute of cotyledons, and ultimately 

 parasitic. 



The Lucerne Dodder. 



Cuscuta hassiaca, Pfeiffer. 



Tbis species was first observed on lucerne in the Canterbury 

 District. The seed had been iin| cited from California. In 

 some parts of tbe field it was most abundant, and had extended 

 its operations to the sorrel, knot-gi ass. and otlur weeds which 

 grew sparingly amongst the crop. Tbe following season the 



