CLIMBING PARASITES. GREEN-LEAVED PARASITES. TOOTHWORT. 171 
however, to mention the fact that the various species of Chytridex and Sapro- 
legniacee do not content themselves with plants that are second-rate hosts, but 
exercise a selection amongst the different green alge living in the water. It is 
astonishing to find that the swarm-spores invariably swim to cells whose protoplasm 
affords the most suitable nutrient basis for them, and attach themselves to those 
cells only, and never on other species unadapted to their requirements. 
CLIMBING PARASITES. GREEN-LEAVED PARASITES. TOOTHWORT. 
The third group into which parasites were divided at the beginning of this 
chapter is composed of flowering plants throughout. According to their method of 
attacking the host for the purpose of absorbing nutriment from it, they range 
themselves in six series. In the following pages we shall discuss the charac- 
teristics of each series as manifested in the most remarkable forms belonging 
to it. 
The first series includes plants destitute of green leaves and of chlorophyll in 
general, whose seeds germinate on the ground and send forth each a filiform stem, 
which brings itself, by means of peculiar movements, into contact with the host- 
plant, coils round it, and develops organs of suction whereby it takes nutriment 
from the plant assailed. 
To this series belong the genera Cassytha and Cuscuta. The former includes 
some thirty species, all of which appertain to warm climates. Most of the Cassy- 
the inhabit Australia, where they attack, in particular, the copses of Casuarinz 
and Melaleuce, fastening their wart-shaped, or, in many cases, shield-like or discoid 
suckers upon the young green shoots of those plants. Several species also are 
indigenous to New Zealand, others’ to Borneo, Java, Ceylon, the Philippines, and 
the Moluccas. South Africa, too, is the home of a few Cassythe, and one species 
(C. Americana) is distributed over the West Indies, Mexico, and Brazil. A 
European, seeing these parasites with their twining, thread-like, leafless stems, and 
their flowers aggregated in capitula, umbels, or spikes, takes them at first to be 
species of the genus Cuscuta, popularly called Dodder. That these plants should 
be most nearly related to laurel-trees is the last thing one would expect. Ex- 
amination of the flowers and fruit reveals, it is true, a close resemblance to those of 
laurel and cinnamon trees, and, therefore, these Cassythz are rightly placed by 
systematic botanists among the Lauracex. But in respect of food-absorption, as in 
general aspect, they are entirely analogous to the various species of the genus 
Cuscuta, which belong to the family of Bindweeds (Convolvulacez). The last- 
named genus is even more variously differentiated than the genus Cassytha, and 
includes about fifty species dispersed pretty evenly over the whole world. Every 
part of the world has its own characteristic forms. One group occurs in California, 
Carolina, Indiana, Missouri, and Mexico, another in the West Indies, Brazil, Peru, and 
Chili, a third at the Cape of Good Hope. Other species are natives of China, the 
East Indies, the steppes of Central Asia, Persia, Syria, the Caucasus, and Egypt. 
