300 



PART IV. — VEGETABLE TAXONOMY. 



vided at its smaller end with two long cilia, by means of which it 

 moves actively through the water. Some of them find their way 

 into the oogonia and fertilize them. See Fig. 499. 

 The ripe spore rests for a time, and then, either 

 in the autumn or early spring, germinates. It does 

 not, however, immediately produce the leafy plant, 

 but develops a differ- 

 ent one, called the 

 pro-embryo. From 

 this the leafy plant 

 springs as a lateral 

 shoot, and the pro- 

 embryo afterward 



perishes. 



a a 



Fig. 499. — Portion of one of the antheridial filaments, magnified about 800 diameters, 

 showing antherozoids in all of the cells but two; from these the antherozoids have escaped, 

 and are shown at a, a. 



CHAPTER VI.— THE THALLOPHYTA. ALG^E (Cont'd). 



THE MELANOPHYCEJE THE FLORIDEjE. 



The Melanophycf.jE or Phcsophycece, as they are aiso called, 

 are all marine plants, and are among the most abundant as well 

 as the largest plants of the ocean. While some are of small size, 

 others attain gigantic dimensions, Macrocystis, for instance, 

 having a length of stem which considerably exceeds that of the 

 tallest Australian Eucalyptus trees and California Conifers. In 

 complexity of structure, also, the group presents great differences, 

 some being quite simple, others among the most complex of their 

 class, but the simplest are connected with the most complex by 

 almost innumerable gradations. 



They all possess, in addition to chlorophyll, a peculiar brown 

 coloring matter related to that found in the Diatoms, and hence 

 they have an olive-green or brownish instead of a bright-green 

 color. They are, on this account, called Brown Sea-weeds. 



Many of them produce swarm-spores, which are peculiar in 

 the fact that the cilia are not located at the colorless apex, as in 



