78 WHAT IS A PLANT? 



III. — Presence of Starch. Protoplasm excepted, the most 

 widely-distributed of al^ vegetable cell-contents is starch ; still, it 

 is not confined to the plant-kingdom. Bernard found it in the 

 liver of the calf and pig — i.e.^ he obtained from them a substance 

 called "glycogen," allied to, if not absolutely identical with, 

 starch. It is also found in the human brain, liver, and placenta ; 

 in the protoplasmic substance of Thalassicolla and other Radiola- 

 rians (a group of Protozoan organisms which secrete shells of 

 exquisite beauty and delicacy), there are minute bodies termed 

 yellow cells. These Haeckel finds to contain starch, * 

 answering at once to the iodine test, and in some cases making 

 up more than half the entire bulk of the animal. Cienkowski 

 (1871) thinks these may be plant-parasites, a possibility requiring 

 further research.f On the plant-side, starch is absent in the 

 Fungi as an order, so far as we know at present. Here again, 

 therefore, we fail in finding a distinction of any real value. 



IV. — Presence of Chlorophyll. This is the green colour- 

 ing matter of plants, occurring usually as fine granules, these being 

 most abundant immediately below the surfaces of leaves ; it is 

 formed only under the action of light, with two exceptions, viz. — • 

 the germinating seeds of some conifers and the fronds of ferns, 

 where, under certain conditions of temperature, its formation goes 

 on in the dark. Chlorophyll, however, like cellulose and starch, 

 has found its way into the animal kingdom. Among Protozoa, 

 it is found in Sfentor, the trumpet animalcule, and as a dense layer 

 beneath the body-surface in two of the Heliozoa — Raphidiophrys 

 and Heterophrys^ discovered by Archer, of Dublin. J Among 

 Porifera, it is abundantly present in Spongilla, the fresh- water 

 sponge. Among Ccelenterata, we find it in Hydra viridis, the 

 green fresh-water polype. Among Turbellarian worms, Mr. P. 

 Geddes discovers it in Mesostomiim viridis, and again in Convo- 

 hiia, the little green Planarian that basks in the sand, and ooze 

 on parts of the Russian coast. § It has also been thought to exist 



* Journal Linn. Soc. Zoology, Vol. XIIL, p. 427. 



f Ibid, Vol. XIV., p. 145. Vide note at end of Part II. of paper. 



X Journal Linn. Soc, Vol. XIIL, pp. 292, 297. 



§ Royal Soc. Proc, No 194. 



