38 



HUTCHINSON'S POPULAR BOTANY 



bodies are known as chlorophyll corpuscles or chloroplasts, and the green 

 colouring pigment chlorophyll a name derived from the Greek chloros, 

 green, and phullon, a leaf. Many millions of such corpuscles exist in every 

 full-grown plant of Vallisneria ; though that circumstance alone is not our 

 warrant for returning to the subject. If chlorophyll were only distributed 

 in the tissues of a few water-plants, it would call for no special mention 

 here ; but the contrary is the case. As a matter of fact, these tiny bodies 

 of coloured matter constitute one of the most widely distributed of vegetable 

 substances, being found in all green plants ; while their essential identity 

 with protoplasm gives them an especial interest. Chlorophyll corpuscles 

 have, indeed, been defined as specialized masses 

 of protoplasm coloured green, and no definition 

 could be more. clear, concise, and satisfactory. It 

 is thought that they possess a reticulated struc- 

 ture, and that the colouring matter occupies the 

 meshes of the network in a state of solution. 

 Chloroplasts are not found in animals, save, in- 

 deed, in some of the Flagellata, Planarians, etc., 

 as a foreign product. The latter exception needs 

 to be recorded, since it was long held that the 

 chloroplasts contained in the tissues of the fresh- 

 and salt-water Sponges, and the fresh-water Polyp, 

 belonged to those animals.* Professor Weiss has 

 shown that they are really vegetable cells which 

 may be cultivated outside the animal body. ' : As," 

 says he, "these green cells can form starch and 

 ultimately sugar, which transfuses out of the Algce 

 into the body of the animal, it is evident that they 

 are of real benefit to the animal, while the Algce 

 themselves can absorb certain substances out of 

 the animal cells. An analogous example occurs in 

 the Vegetable Kingdom in the case of the Lichens, 

 in which some green Algce are associated with a 

 Fungus. Every Lichen consists of the two 



different organisms, and the green cells form, under the influence of light, 

 food substances which are made use of by the Fungus. In initial stages 

 the Fungus can be seen capturing, with its threads, the Algce cells 

 of which it makes use, and which are the working partners of the 

 concern " f (fig. 61). 



Some minute marine-worms (Tarbdlaria), known as Convoluta, have 

 established a remarkable partnership with some of these green single-celled 



Chlorophyll corpuscles were found in fresh-water Sponges by Sir E. Ray Lankester, 

 and Mr. MacMunn found them in no less than nine specimens of sea Sponge. 

 T Proceedings of the Manchester Microscopical Society, 1892. 



FIG. 61. SECTION THROUGH 



A THALLUS OF LICHEN 



(Sticta fuliginosa). 



Magnified 500 times. 



