and its relation to that in the Animal Kingdomt 353 



of formation, whose product is the frond." Iloftncister has 

 recently seen* the speri/ialozoids penetrate thronr/h the attenuated 

 and softened membrane of the central cell of the arche(jonium, into 

 its interior, and then for a time move round the free part of the 

 germinal vesicle. The inner end of the canal of such archegonia 

 appeared closed by the subsequent expansion of the surrounding 

 cells, — the first sign of fecundation having taken place. 



Equisetaci;.!:. — The so-called germination of the spores of the 

 Equiseta had been long ago minutely investigated, especially by 

 Agardhf, Vaucher J, and Bischoff §, but it vras only after the dis- 

 covery of the antheridia of the Ferns had excited new conjec- 

 tures, that the antheridia were observed in the irregularly lobed 

 prothallium of the Equiseta, first by Thuretjl, and afterwards 

 by Milde^ and Hofmeister**. They occur upon the border of 

 the prothallium, as conical, cellular papillse, not definitely sepa- 

 rated from the prothallium, but with their bases imbedded in it ; 

 the cells of their simple envelope are directly continuous \^ith 

 the upper layer of cells of the prothallium. The nucleus con- 

 sists, in the young state, of small cubical cells, in which are 

 formed spiral-thread-producing vesicles, in the same way as in 

 the Ferns. "When perfectly ripe, they open by the separation 

 from each other of the upper cells of the envelope, which remain 

 connected with the lower cells only by their inferior walls, and 

 surround the orifice like a crownff. The spermatozoids are larger 

 than those of the Ferns — in fact, are the largest hitherto met 

 with in plants, and consist of a band-like body, wound like a 

 corkscrew, furnished with numerous cilia at the anterior ex- 

 tremity. The posterior extremity, in contrast to that of all 

 other known spermatozoids, is much spread out. 



The emission of the spermatozoids from the spermatic vesicles 

 is often imperfect, as occurs also in the Mosses and Ferns ; the 

 vesicle then remains hanging on the anterior or posterior ex- 

 tremity of the spermatozoid, and is carried along by it. 



The first notice I find of the detection of a (dead) archegonium 



* Flora, 1854, p. 257. (Ann. Nat. Hist. 2nd ser. xiv. p. 273.) 



t Observ. snr la Germination des Preles. Mem. du Museum, Paris, ix. 

 p. 283 (1822). 



;|; Monogr. des Preles. ]Mem. de la Soc. phys. &c. de Geneve, i. pt. 2. 

 p. 347 (1822). Mem. siu* la Fructification des Preles. Mem. du Museum, 

 Paris, X. p. 429 (1823). 



§ Krvptog. Gewacbs. Nuremberg, 1828. — Ueb. Entw. d. Equiseteen. 

 Nova ActaL. C. N. C. xiv. pt. 2. p. 779 (1828). 



II Ann. des Sc. nat. 3 ser. xi. p. 10 (1849). 



^ Zm* Eat\A-ickl. der Equiset. u. Rhizocarp. Nov. Act. xxiii. pt. 2. p. 630. 

 De Sporarum Equiset. Germinat. Linnsea, xxiii. p. 558 (1850). 



** Vergleicb. Uutersucb. &c. p. 100. 



tt See Tburet's figure, Aun. des Sc. nat. 3 ser. xvi. pi. 15 (1851). 

 Ann. ^ Mag. N. Hist. Ser. 2. Vol. xx. 23 



