AXTHEKIDIA OF FERNS. 359 



upon the middle of a slightly-arched prothallium cell (p), and 

 is cut off from it by a partition membrane. The wall of the 

 antheridium consists, almost without exception, of two tiers of 

 superposed undivided annular cells (1 and 2) and a lid cell (3). 

 The side-view of an emptied antheridium (Fig. 131, B) shows the 

 annular cells very strongly swollen ; they therefore stand out 

 more clearly. Comparison with the surface view shows plainly 

 their unsegmented character. 



The Spermatozoids. If we have for examination prothallia 

 which have not been wetted for some time, we shall not have 

 long to wait for the dehiscence of ripe antheridia. The .mechan- 

 ism of evacuation consists in the pressure which the annular 

 wall cells bring to bear upon the contents, besides which a 

 swelling substance is developed between the separated internal 

 cells of the antheridium. The lid-cell is ultimately ruptured 

 and the contents of the antheridium squeezed 

 out, the annular cells then increasing in size. 

 The contents of the antheridium come out 

 in the form of isolated, globular cells, the 

 spermatozoidal cells, which first lie quies- 

 cent for a short time in the surrounding FlG 132. Spermato- 



water. In each cell, even with a low power, zoid of Phegopteris fixed 



r ' with osmic acid vapour 



is to be recognised a coiled thread, the and stained with fuchsin 

 spermatozoid (antherozoid), and a central ^S^^^S 



collection of fine granules. The walls of nucleus, k ( x 540). Com- 

 ,.,?, ,. pare with Chara,Fig. 113. 



these cells dissolve in the surrounding water, 



and even in a few seconds individual spermatozoids begin 

 to free themselves. This occurs with a jerk, whereby the 

 coils of the body of the spermatozoid separate. One sperma- 

 tozoid after another thus escapes. We follow individuals in 

 the surrounding water, and notice that they progress com- 

 paratively rapidly, and at the same time rotate upon their 

 axis. After about twenty to thirty minutes, the movement 

 slackens, and finally ceases. During these last stages of the 

 movement, the form of the spermatozoid is not difficult to recog- 

 nise. This is more easily done if to the drop of water containing 

 the spermatozoids is run in a little 10 per cent, clear filtered 

 solution of gum-arabic, and the rapidity of their movement thus 

 diminished. The spermatozoid (Fig. 132) is composed of a 

 band, coiled corkscrew- wise. The coils at the anterior end are 

 narrow, but towards the posterior become broader. The anterior 



