CELL FORMATION BY UNION. 



masses come in direct contact by means of a tube (the pol- 

 len tube) which touches with its lower extremity the embry- 

 onic vesicle. 



(a) The foregoing classification of the modes of cell -formation differs 

 in many respects Irom that given by Sachs in the fourth edition of his 

 " Lehrbuch." His classification as there given is as follows : 



. 



Fig. 3S. Vtiucheria sessilis. A, origin of the lateral branches, on (mgnnhm), and 

 h (anttifridium), from the filament ; B, the branch a (the same as h in A) has its ter- 

 minal portion cut off by a partition ; in ng the protoplasm is becoming greatly con- 

 densed ; C. the same as o<i of B. but further advanre-1 (now called an oosphere) and 

 the wall burst open, permitting the escape of a drop of mucilage si ; 1), small motile 

 cells (sprrinatozoids) from the terminal cell of a in li ; E, the samo as C, but a little 

 later the spermatozoids are entering through the opening ; F. a, the branch a in B, 

 with the terminal cell now empty, on account of the escape of the gpermntozoids ; 

 o*p, the same as E, and og in B, after union with tho spermatozoids the protoplasm 

 is surrounded by a tbick cell-wall and it is now called an oospore. X 100. After 

 Sachs. 



A. FORMATION OP REPRODUCTIVE CELLS. 



1. Rejuvenescence. 



2. Conjugation. 



3. Free Cell-Formation. 



4. Formation of Reproductive Cells by Division, which is made to 

 include the formation of pollen, the spores of mosses and frrns, and 

 the conidia, stylospores, and basidiospores of many fungi. 



