I08 CLASSIFICATION OF PLANTS 



cells are minute non-motile '^spermatia," cut off from the tips 

 of certain branches. The female branch, carpogonium, is ter- 

 minated by a slender filament, the trichogyne. When a sper- 

 matium comes in contact with this trichogyne a fusion takes 

 place which effects a fertilization. The result is that by a more 

 or less indirect process spores, carpospores, are developed 

 farther down on the branch. 



249. Class 9. Phycomycetes. — The Phycomycetes are fungi, 

 that is, they contain no chlorophyll and are therefore sapro- 

 phytic or parasitic in habit. But in many other respects they 

 resemble algae, especially the Siphonales. The thallas is tubu- 

 lar with few or no cross walls dividing it into cells, and the proto- 

 plast contains numerous nuclei. Spores are formed asexually 

 by the division of the protoplasmic contents of a sporangium. 

 These spores are motile in aquatic forms but those of terrestrial 

 forms are simple rounded cells which are scattered like dust. 

 In some genera a kind of spore, conidium, is formed by the 

 cutting off of a cell from the tip of a filament (hypha). 



2 50. Order i . — The Oomycetes reproduce sexually by means of sperm and 

 egg cells. In some cases the sperm cells are motile spermatozoids which 

 are set free from an antheridium, make their way to the oogonium and 

 fuse with the egg cell producing an oospore. In most cases, however, 

 the antheridium forms a tube which grows toward and into the oogonium. 

 In this case the sperm cells are not provided with flagellae. They pass 

 through the tube of the antheridium directly into the oogonium and there 

 reach the egg cell. The asexual spores are swarm spores. The oomycetes 

 grow as saprophytes in fresh water or as parasites in plants and, occa- 

 sionally, animals. 



251. Order 2. — The Zygomycetes reproduce sexually by the fusion of the 

 contents of two similar gametangia. The resulting body is called a zygo- 

 spore. The asexual spores are produced either in sporangia or as conidia. 

 The Zygomycetes are terrestrial and grow as saprophytes on vegetable or 

 animal matter or as parasites in insects. The black mold on bread, etc., 

 is a familiar example. 



252. Class 10. Basidiomycetes. — The Basidiomycetes are 

 distinguished by the club-shaped basidium upon which four 



