37 



LECTURE XXI7I. 



shoots above the surface. This is the case with Neoltia, Epipogon, Corallorrhi'za, 

 and Monotropa-, and it is still to be remarked that in the case of Corallorrhiza 

 the vegetative body lying in the humus is a rootless, branched shoot, while in 

 Monolropa, on the other hand, it is, according to Kamiensky, at first a shootless, 

 branched root-system, out of which the flowering shoots spring later, like the fructifica- 

 tion from a mycelium. 



With respect to the nutritive processes in question here, only very little is known, 

 however, in the case of parasitic Phanerogams. In the first place, so much is at any 

 rate established, that they are not able to produce starch by the decomposition of 

 carbon dioxide ; for this, not only is the chlorophyll wanting, but light also, during 

 the greater part of the period of vegetative activity in the majority of parasites and 

 humus plants; for these plants, apart from Cuscufa, only allow their flowering shoots 

 to protrude free from the substratum at the very last, when the entire mass of organic 

 substance is already wholly or for the most part collected. Where then, as usual, we 

 find considerable quantities of starch and other carbo-hydrates in parasites and 

 humus plants containing very little or no chlorophyll, this is owing in no case to the 

 activity of the chlorophyll in the plants in question ; on the contrary, the starch and 

 other carbo-hydrates are here derivatives of those chemical compounds which have 

 been dissolved and taken up from the host-plants, or, in the case of the humus plants, 

 from the remains of dead plants. With respect to the proteid substances of these 

 plants which contain little or no chlorophyll, these may according to circumstances 

 likewise be derived from the host-plant, or, as may be supposed, are first formed in 

 the tissues of the parasite. When, for example, the entire vegetative body, up to the 

 development of the flowers, developes within the host-plant, as in the Rafflesiaceae, 

 it may be assumed that here not only the non-nitrogenous but also the nitrogenous 

 vegetable substance of the parasite is absorbed from the host-plant ; and the same may 

 be the case in Cusciita, since this parasite, slung around the host-plant, possesses no 

 roots at all in the soil, and therefore extracts the whole of its food from the host. It 

 may at least be otherwise in the Orobanchese. These parasites are firmly fixed by 

 a haustorium to their host-plant, and without doubt extract the whole of the 

 carbonaceous substance which they require from the host, but they also produce 

 several roots besides ; these roots are short, it is true, but they penetrate into the 

 earth, and the surface of the shoot is, like that of the Balanophorese, for a long time 

 in contact with the surrounding soil : they may thus take up ash constituents and 

 probably saltpetre also from the earth, the nitrogen of which is possibly employed 

 for the formation of proteid substances in the tissue of the parasite. 



One of the most important questions is, how does the parasitic Phanerogam 

 commence to absorb from its host-plant the substance assimilated by the latter? 

 It is to be observed in the first place that the union of the parasite and host is 

 usually very complete, so much so indeed that it requires the most careful examina- 

 tion to discover the limit between the tissues of the parasite and those of the 

 host-plant. The Rafilesiacese, completely enclosed in the tissues of the host-plant, 

 behave, in fact, as if their vegetative body were simply another form of tissue in 

 its interior : the sharp distinction between parasite and host only begins on the 

 development of the flowers. The fact is here of the utmost interest that the nutritive 

 substances which the parasite takes up from the tissues of the host-plant nevertheless 



