CELL FORMATION BT UNION. 



47 



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 : 





?PPJ: 





Fig. 38. — Vauchena sessiliB. A, oriein of the lateral branches. 07 {oogoniimi), and 

 h (antheridium), frnm The filnment ; B, the branch a (the pame as h in J.) hfif its ter- 

 minal portion cut o£E by a partition ; in 017 the protoplasm is becoming grently con- 

 densed ; C, the same as 00 of B. but further advancei (now called an oosphere) and 

 the wall burst open, permitting the escape of a drop of mucilHge »l.; JD, small motile 

 cells (spermatozoids) from the terminal cell of a in 5 ,• JS, the same as C, but a litfl© 

 later— the spermaiozoids are entering through the opening ; J*, a, the branch a in B, 

 with the terminal cell now empty, oh account of the esrape of the sperraatozoids ; 

 o/ip^ the same as E^ and og in B, after union with the sperraatozoids— the protoplasm 

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

 Sachs. 



A. —Formation of 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 ferns, and 

 the conidia, stylospores, and basidiospores of many fungi. 



