Development of the Anthendmm in Ferns. 235- 



Tliuret* conceived the structure of the antheridia quite dif- 

 ferently from all previous observers, and, as we shall soon see, 

 was the first to take a correct view of them. In most Poly- 

 podiacea3 they consist, according to him, of three superimposed 

 cells — a peduncular cell, which attaches the organ to the pro- 

 thallium, an annular cell, Avhich encloses the mother cells of 

 the spermatozoids all round, and a terminal opercular cell. 

 In many cases the inner space of the antheridium reaches 

 down to the surface of the prothallium, so that the basal cell 

 also becomes an annular cell-. How these annular cells are 

 produced, whether they are formed as such at once, or owe 

 their origin to the coalescence of several cells, is a question 

 which Tliuret leaves untouched. 



Mercklinf, who, of all the observers hitherto mentioned, 

 had the most abundant material at his disposal, follows Niigcli 

 essentially in the interpretation of his observations, and rejects 

 Thuret's conception (p. 18); whilst Mettenius| unconditionally 

 agrees with the latter, and refers only to Thuret with regard 

 to the structure of the antheridium. 



According to Hofmeister§, there occurs in the mother cell 

 of the antheridium a division by an inclined partition, either 

 immediately or after one or (rarely) more divisions have taken 

 place in it by transverse septa. The newly formed cell of the 

 second degree divides at once by a radial longitudinal wall. 

 After a single repetition of the division of the apical cell by a 

 septum inclined in an opposite direction, the longitudinal 

 growth of the antheridium ceases. The second cell of the 

 second degree is also divided by a radial septum into two 

 parts, of the form of quadrants of a cylinder. Next one of the 

 cells of the third degree is divided by a septum parallel to the 

 longitudinal axis of the organ, and cutting the side walls at 

 an angle of 45°. The antheridium now forms a semiglobular 

 cellular body, consisting of a four-sided central cell filled with 

 granular ])lasma, supported by one cylindrical or two semi- 

 cylindrical cells, envelo])ed by four cells of the form of seg- 

 ments of a cylinder, and covered by a cell of the form of the 



segment of a sphere The cells of the antheridium which 



embrace the central one increase no further. The central 

 cell, on the other hand, after considerably increasing in size, 

 in consequence of which the cells surrounding it are flattened 



* " Siir les Antheridies des Fougeres," Ann. Sc. Nat. ser. 3. tome xi. 

 (1849) p. 7. 



t Beobaclitungen au dem Prothallium der Farrnkriiuter (ISoO), p. 12 

 et seqq. 



X Beitrag-e ziii- llotanik (18,50), p. 22, 



§ Vergleicliende Untevsuchungen, &c. (18-51) p. 70. 



IG-' 



