THE PHYLOGENY OP THE FUNGI 629 



cells with flagella or cilia or produce such cells for the purpose of multi- 

 plication it seems logical to conclude that the ancestors of these groups 

 were unicellular, motile organisms. They must have been already highly 

 developed in their cell structure for we find in the green algae, lower fungi, 

 and animals essentially the same basic nuclear structure, sexual repro- 

 duction whose fundamental phenomena are the union of two haploid 

 nuclei into a diploid nucleus followed sooner or later by meiosis, and 

 similar laws of heredity. Therefore we must believe that the forms an- 

 cestral to these three lines had already reached the height of development 

 attained by the unicellular, motile or zoospore-producing algae. The 

 sulphur or iron bacteria mentioned above lack such definite nuclei and are 

 much too simple in structure to have been the immediate ancestors 

 sought. 



It appears to the author that probably the lines of evolution after the 

 invention of chlorophyll progressed rapidly in various directions. The 

 known Myxophyceae have not reached the type of cell structure that 

 could have given rise immediately to the unicellular, flagellate green algae 

 or to the lower fungi or animals. It is to the organisms more like the simple 

 chlorophyll-bearing flagellate algae that we must turn in our search. In 

 such algae we have a constant production of organic material, by means of 

 photosynthesis, and thus chlorophyll-lacking organisms could develop, 

 depending upon them either directly or indirectly for their food. We find 

 that the motile organs of such simple alga-like organisms as we now know 

 are usually one to four in number, connected to little organelles, the 

 blepharoplasts, at or just below the plasma membrane, these usually being 

 then connected to the nucleus. Evolution led to the production of two 

 main types of flagella. In one type there is a firmer outer tubular envelope 

 surrounding a softer more flexible portion which extends beyond this 

 outer portion and is capable of very active lashing motion. These are the 

 "whiplash" flagella. Another type consists of a much more flexible axis 

 from whose sides arise at right angles numerous very fine cilioles which are 

 capable of movement. This is the "tinsel type" of flageflum. Some of the 

 single-celled plants possess one or more of the one type or of the other 

 type, but in one group of algae one flagellum of each type occurs. This is 

 the group called Heterocontae or Xanthophyceae. Here the flagella may 

 be equal in size but usually with the tinsel flagellum directed anteriorly 

 and the other turned back. The latter is frequently shorter and in some 

 cases appears to be lacking. 



Another characteristic of the unicellular algae is the fact that the 

 motile cells do not normally produce a true cell wall, the outer layer being 

 simply a plasma membrane. This becomes encysted with a true cell wall 

 which serves as a protection. In the further evolution of the various 

 groups of algae the encysted stage becomes the normal vegetative condi- 



