50 



THE YOUNG NATURALIST. 



conditions of plant life and growth 

 must now be pretty familiar. It is 

 known that the nutritive materials are 

 derived partly from the soil by the 

 roots, and largely from the atmosphere 

 by the leaves. That in the wonderful 

 vital laboratory of the leaves, chiefly 

 by the action of the chlorophyll, i.e. 

 the green colouring matter, under the 

 influence of light, the raw inorganic 

 material is elaborated or manufactured 

 into organic substance, out of which 

 the tissue of the plant is built up, in 

 other words the material or food is 

 digested, and the plant grows. But 

 in true parasites the power of assimilat- 

 ing inorganic material is wholly lost, 

 and the plant is entirely dependent 

 for its supplies upon the already 

 digested and assimilable stores of 

 its "host" into whose tissues it drives 

 its roots and absorbs its juices. Hence 

 we find in plants in which the parasitic 

 habit has become confirmed, as leaves 

 are useless they have been dispensed 

 with, and there is an entire absence of 

 the vitally active chlorophyll, therefore 

 they are leafless, devoid of all green 

 colour, and of a dusky brownish hue. 

 Most people have a very hazy idea 

 as to what a parasite is like, and even 

 those who ought to know better have 

 very indistinct notions about these 

 abnormal plants. For instance a 

 student who presented himself for 

 examination in Botany under the 

 Science and Art Department, gave 



Brussels Sprouts as an example of 

 parasite ! It is easy to laugh at such 

 ignorance, and yet the peculiar 

 excresences which are the characteristic 

 of Brussels Sprouts, and which are so 

 justly and highly esteemed as a culinary 

 delicacy might easily enough pass 

 muster as a parasitic outgrowth by 

 wiser folks than this embyro botanist. 



The most of well-informed people 

 have an idea that the mistletoe is a 

 parasite ; but if they were asked to 

 say if there were any others, or how 

 many parasitic native plants we have, 

 they might find it difficult to name 

 another, although there are in reality 

 at least half-a-dozen genera, including 

 nearly three times as many species, in 

 which the parasitic habit has become 

 so established that they are now un- 

 able to maintain an independent exis- 

 tence. Besides these, there are a large 

 and increasing number in a transition 

 state, deriving part at least of their 

 food supplies from already organised 

 material. Flowering parasites may be 

 grouped in two classes — (i.) stem par- 

 asites, (ii.) root parasites, according to 

 their place of growth on their " host " 

 —that is, the plant which involuntarily 

 provides them with food and lodging. 

 Foremost of these is the familiar 

 mistletoe, which was fully described in 

 vol. ii. of the Y.N., and here only 

 requires a brief recapitulation of its 

 leading features. It is essentially a 

 stem parasite, and has so completely 



