152 Dr. H. Franklin Parsons on the 



having been shown us at a recent meeting by Mr. Mennell. These 

 plants all agree in the absence of chlorophyll, and are hence more 

 or less self-coloured and of a dull brown hue, ranging, however, 

 from shades of purple to yellow ; they are of a succulent nature, 

 and the roots are few and fleshy ; the leaves are reduced to mere 

 scales ; the stems are simple, except in one Orobanche ; and the 

 flowers are in terminal spikes. Most of these characteristics 

 obviously depend upon the circumstance that such parasites 

 obtain their organic constituents ready made from other plants, 

 instead of manufacturing them for themselves by the aid of their 

 leaves from the carbon dioxide of the atmosphere. 



There is another group of plants, however, which, though 

 partially at least parasitic on the roots of other plants, are never- 

 theless green and leafy. This group includes the genera Pihin- 

 anthus, Bartsia, Etqjhrasin, Pedicularis, and Melampyrum, in the 

 order Scrophulariacefe. It is to be remarked that in these plants 

 the leaf area is small in proportion to the size of the plant, and 

 that of several of them the colour is a pale yellow-green {e.g., 

 Fihinanthus Crista-galli and Bartsia viscosa). Several of them 

 have an upright uubranched stem and flowers in terminal spikes 

 like the leafless root-parasites. We seem to have in these 

 genera plants more or less on their way to the mode of Ufe which 

 such plants as Orobanche have completely acquired. 



It may be remarked, that of our two British aerial parasites 

 the dodder is leafless and not green ; while the mistletoe is still 

 leafy and green, though the leaf area is small compared with 

 many other shrubs, and the leaves are of a pale yellow-green. 



2. Another type of plants inhabits the gravelly bottoms of 

 the shores of pools, especially mountain lakes. It has narrow, 

 stiff, quill-like root-leaves, with no stem except the scape which 

 bears the flowers. The most characteristic plants of this habit 

 are the following : — Awlwort {Subidaria aquatica), Cruciferae ; 

 water-lobelia {Lobelia Dortmanna), Campanulacese ; shoreweed 

 {LittoreUa lacustris), Plantaginaceae ; quillwort [Isoeteslacustris], 

 Lycopodiaceae. In addition to these several species of rushes 

 and sedges may be found inhabiting similar situations and 

 having much the same habit of growth ; but in their case this 

 habit does not differ widely from that which is general in the 

 orders to which they belong. The four first-named plants, how- 

 ever, belong to widely separated orders, and differ greatly from 

 the general habit of these orders, but resemble each other so 

 closely that from the foliage alone it is not easy to tell them one 

 from the other. The stout quill-like form of the leaves is doubt- 

 less advantageous in enabling them to withstand the shock of 

 the miniature waves on the lake-shore, while they are also stiff 

 enough to stand erect in air when the bottom of the lake is left 

 uncovered bv the water during dry seasons. 



