OF ALG.E. 



143 



in a group of plants, upon placing the whole colony under the 

 microscope. 



We have already had before our eyes two methods by which 

 plants rise from a lower to a higher rank, namely, by the formation 

 of distinct cells in a continued series, and by the specialization 

 of parts for a particular function. The complication is still fur- 

 ther increased by the development of cells in a lateral direction, 

 so as to form a leaf-like plant. The common, light green, parch- 

 menty sea- weed, Ulva, everywhere upon our rocky coast known 

 under the name of green Dulse, or Laver, is an example of this 

 kind; and the olive-colored, or brown, leather-apron-like sea- 

 weed, Laminaria, exemplifies the increase of growth of cells, not 

 only longitudinally and transversely, but at right 

 angles to the latter direction. In this whip-cord- 

 like plant, (fig. 85, A,) known in science as Chor- 

 da, which is very common in rocky bays, the 

 lateral growth of cells is such as to produce a 

 round figure, from slender base to tapering tip. 

 The spores (B, C) resemble those of Saprolegna, 

 but have a red eye-spot. According to Thuret's 

 observations, they are developed in the superficial 



cells of the cord This, I think, will suffice to il- 



ci 



lustrate the tendencies of the march of develop, 

 ment from the lower toward the higher forms of 

 plant-life, as contrasted with a similar procedure 

 among the inferior grades of animal life, which I 

 have described to you in a former lecture (pages 

 9 to 14). But let us now turn again more particularly to the 

 supreme result of these investigations, which was to show that 

 certain kinds of so-called Infusoria were not animals but plants. 

 Here, then, was a new set of phenomena to be investigated 

 by the physiologist. Zoologists said at once that the fact that a 

 body moved from place to place was no longer a criterion of its 

 animality ; nor could they fall back upon another fact, which 



Fig. 85. Chorda filum. A, a plant; B, C, zodspores, magnified 330 diameters. 

 B, C,from Thuret. 



Fig. 85. 



