BOTANY 



e ..... 



f 



r n 



n 



FIG. 1. A, Kuglena viridis, a green 

 Flagellate; e, eye-spot; v, contractile 

 vacuole; n, nucleus; /, flagellum 

 (X 700). B, a colorless Flagellate, 

 Bodo caudatus, attacking a ciliated 

 green plant, Chlamydomonas ; lettering 

 as in A (X520). (After BUTSCHLI.) 



the cells of animals and plants is perhaps the strongest evidence, to 

 the biologist, of the intimate connection between all living things. 



The Cell. With few exceptions the protoplasm is segregated into 



masses of definite form known as cells, and each cell contains an 

 organized body, the nucleus, while in many plant-cells, other parts 

 like the cell-wall and chromatophores are present. The character of 

 the cell-plasma, or cytoplasm, and that of the nucleus of the animal 

 and vegetable cell are extraordinarily similar, and this is true, also, 

 of the phenomena connected with the formation of new cells. 



The Simplest Forms of Life. The lowest organisms are often so 

 slightly differentiated that it is not possible to assign them positively 



to either the animal or vegetable 

 kingdom ; indeed, there is much 

 diversity of opinion as to the 

 affinities of many of these simple 

 forms. Most of these exhibit 

 active movements, and at first 

 sight would be at once classed as 

 animals. Many of them, how- 

 ever (Fig. 1 A), possess green 

 chromatophores, and in other re- 

 spects show unmistakable plant- 

 affinities. It is not at all unlikely 

 that some existing forms are real- 

 ly intermediate in character, and 

 resemble the common ancestors 

 from which the two great organic 

 kingdoms may have diverged. 

 The presence of chlorophyll may be considered a strictly vegetable 

 characteristic. Where chlorophyll occurs in the body of animals, 

 e.g. Hydra viridis, fresh-water Sponges (Spongilla), various Infusoria, 

 etc., it has been shown that the chlorophyll belongs to minute 

 unicellular plants (Algae) which are associated with the animal. 

 Where chlorophyll is certainly present in the cells of an organism, 

 its vegetable nature may be pretty safely assumed. However, as we 

 .have already seen, many unmistakable plants are quite destitute of 

 any chlorophyll. 



The Cell-wall of Plants. Another character common to all typical 

 plants is the substance composing the cell-membrane. The cells of 

 most plants are surrounded by a definite membrane, which in its early 

 stages, at least, is made of a characteristic carbohydrate, cellulose, 

 much resembling starch in its chemical composition. In some cases, 

 especially among Fungi, the cell-wall is composed of a substance dif- 

 fering slightly from ordinary cellulose, and among the Bacteria a 

 true cellulose membrane is rare, although it sometimes occurs. 



