IX FIUCINEAl LEPTOSPORANGIATJE 319 



has the pointed apex cut off by a curved wall from the central 

 cell. The primary neck canal cell, so formed, is noticeably 

 smaller than that of Marattia. The neck cells, which in the 

 eusporangiate forms all grow alike, here show a difference, and 

 the two anterior rows develop faster than tlie posterior ones, so 

 that these rows are longer and the neck is strongly bent back- 

 ward. In Onoclea there are usually about seven cells in each 

 anterior row and about two less in the posterior ones. The 

 neck cells are almost colourless, with distinct nuclei, and a few 

 small, pale chloroplasts. From the central cell is now cut off 

 the ventral canal cell, which is quite small, and separated from 

 the tgg by a strongly concave wall. The nucleus of the neck 

 canal cell always divides, but no division wall is formed, and 

 the two nuclei lie free in the cell. The basal cell divides by 

 cross-w^alls into four, and with similar cells cut off from the 

 adjacent prothallial tissue constitutes the venter of the ripe 

 archegonium. The disintegration of the division avails of the 

 canals cells, and the partial deliquescence of the inner walls of 

 the neck cells, offer no peculiarities. 



When the archegonium opens, the terminal cells diverge 

 widely and the upper ones are often thrown off. 



The opening of the sexual organs and the entrance of the 

 spermatozoids may be easily seen by simply allowing the plants 

 to remain slightly dry for a few days until a number of sexual 

 organs are mature. If these are now placed upon the slide of 

 ^the microscope in a drop of water, in a few minutes the sexual 

 organs will open, and the spermatozoids will be seen to be 

 attracted to the archegonia in large numbers, and with care 

 some of them may be followed into the neck and down to the 

 central cell. The actual entrance of the spermatozoid into the 

 Qgg has been observed, but is difficult to demonstrate in the 

 living condition. Pfeffer (3) has shown that the substance 

 which attracts the spermatozoids in the Polypodiace?e is malic 

 acid, and that an artificial solution of this, of the proper 

 strength, will act very promptly upon the free spermatozoids of 

 these Ferns. 



Buller ( I ) has found that in addition to malic acid and its 

 salts, many salts, both organic and inorganic, which occur in 

 the cell-sap, may exert a positive chemotactic stimulus upon the 

 spermatozoids of Ferns. How^ever, none of them react so 

 strongly as malic acid and its. salts. 



