CELL FORMATION BY 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 Yesicle. 



{a) The foregoing classification of tlie modes of cell-formatiou differs 

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

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



H 



ftffi 



>i'i 





^'C-O;; 



o^'8Y^'Wo'';^^^^^£^ : 



Fig. 38 —Vati^heria sessUia. A, orierin of ttie lateral branchea. Ofj (oogonlwm), and 

 h (ant/teridium)^ from, the filament ; B, the branch a (the same as ^ in A) has it^ ter- 

 minal portion cat off by a partition ; in nq the protoplasm is becoming grently con- 

 densed; C the same as 0(7 of 5. but further advanoefi fnow called an oos^j^ere) and 

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

 cells ((^permatozoids) from the terminal cell of a in i* ; B, the same as C, but a litile 

 later— the spermatozoids are entering throuEh the opening ; F, a, the brnnch a in B, 

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

 Ofif7, the same as JBJ, and og in B, after union with th'^ spermatozoids— the protoplasm 

 is surrounded by a tliick 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 ferns, and 

 the conidia, stylospores, and basidiospores of many fungi. 



