50 PLANT-LIFE 



gonium are somewhat more advanced than the zoospores 

 and gametes of Ulothrix. It will be remembered that 

 in U. zonata the zoospores possess but four cilia, while 

 in (Edogonium they have numerous cilia arranged as a 

 sort of fringe. The gametes of Ulothrix have only two 

 cilia, and in this and other ways they seem to represent 

 more nearly a type of organism closely connected with 

 the ancient beginnings of plant-life on our earth. 



Evolutionists are trying to discover organisms which 

 are survivals of those from which both animals and 

 plants had their origin; and there is a degree of agree- 

 ment that minute flagellated protoplasmic organisms, 

 which cannot be classed either as animal or vegetable, 

 are the modern representatives of ancient life-forms 

 that lived in water, and which have branched off into 

 animals on the one hand and plants on the other. The 

 zoospores and gametes of Ulothrix seem to indicate such 

 an origin for many of the Algee ; but it is not easy to trace 

 all green plants back to such an ancestry. But we must 

 study one or two life-forms in order that we may see their 

 bearing upon this interesting topic. 



In Fig. 17 we have a drawing of a minute organism, 

 Euglena viridis, which some of us may be disposed to 

 regard as a modern survival of a stage in the series of 

 stages which led up to some, if not all, green plants. 

 Euglena is found in puddles, ditches, and ponds, some- 

 times in such numbers as to give the water a green tint. 

 A single individual is not more than ^ inch long. A 

 goodly company can disport themselves as freely in a 

 drop of water as a similar number of full-grown men in 

 a large swimming-bath. A normal specimen is cigar- 

 shaped, furnished with a single flagellum, by means of 



