Development of the Antheridium in Ferns. 235 



Tliuvot* conceived tlu; .structure of tlic antlieridia quite dif- 

 fcrently t'mm all previous observers, and, as avc shall soon see, 

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

 ])odiaceai they consist, according to him, of three superimposed 

 cells — a ])eduucular cell, which attaches the organ to the pro- 

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

 the spermatoztjids all round, and a terminal oj^ercular 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 annidar 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 Thuret leaves untouched. 



]\rercklint, who, of all the observers hitherto mentioned, 

 had tlu' most abundant material at his disposal, follows Nageli 

 essentially in the interpretation of his observations, and rejects 

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

 agi-ees with the latter, and refers oidy to Thuret Avith regard 

 to the structure of the antheridium. 



According to IIofmeister§, 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, enveloped 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 



• "Sur les Antb^ridies des Fougeres," Anu. Sc. Xat. st5r. 3. tome xi. 

 (1849) p. 7. 



t Beobachtungen an dem Protballium der Farmkrauter (1850), p. 12 

 d seqq. 



X lieitrage zur Botanik (18o0), p. 22, 



§ Yergleicbeude Untersucbiinpeu, &c. (1851) p. 79. 



IG* 



