354 Dr. L. Radlkofer on Fecundation in the Vegetable Kingdom, 



on the prothallium of the Equiseta is by Mettenius*. Hofmeis- 

 terf and MildeJ had figured rudiments of archegonia in their 

 earlier essays ; subsequently these two observers simultaneously 

 discovered them in a developed condition on prothallia which, 

 after various, often unsuccessful attempts, they had raised from 

 the spores; Milde in Equisetum Telmateia^, Hofmeister|| in 

 Equisetum arvense {pratense and variegatum). 



In the species hitherto observed the archegonia are ordinarily 

 developed, and at a comparatively late period, on separate pro- 

 thallia^, not bearing antheridia at the same time, distinguished 

 by more vigorous vegetation, or at least upon separate, latere 

 formed shoots of the prothallium **. They originate at the border 

 of the prothallium, but by the continued development of the. 

 mass of the prothallium under them, they are ultimately brought 

 upon its upper surface. Their structure is essentially the same 

 as in the Ferns ; their course of development is as follows tt •■"" 

 A cell of the surface of the prothallium bulges outwards and 

 divides into two superposed cells by forming a septum parallel 

 to the surface of the prothallium. The lower cell of the two is 

 the central cell of the archegonium ; the upper cell is divided by 

 two septa at right angles to each other, but perpendicular to the 

 upper surface of the central cell, into four cells, which by re-, 

 peated division by horizontal septa, form the cyhndrical neck of 

 the archegonium, consisting of four collateral rows of cells. The 

 cells bordering on the central cell, dividing many times, form one 

 or two epithelium-like layers of cells surrounding the central cell. 

 The cells at the apex of the neck of the archegonium elongate more 

 than the lower ones, and curve back, after the formation of the 

 archegonial canal (by the separation of the four rows of cells at 

 their common commissure), like the top of the stigma of a Cam- 

 panula, In the very earliest stages of development of the arche- 

 gonium, a free daughter-cell — the germinal vesicle — is formed 

 round a secondary nucleus in the central cellJt. That part of 



* Beitrag. zur Botanik, Heft 1. Heidelberg, 1850, p. 22. 



t Vergleich. Untersuch. Leipsic, 1861, pi. 20. figs. 61, a, 6, & 62. 



X Op. supra cit. pi. 59. fig. 4/, «. 



§ Das Auftreten der Archegon. am Vort. von Equiset. Telmateia, Ehr. 

 Flora, 1 852, p. 497. (Aug. 28. From a private letter to Prof. Schleiden, 

 accompanied by a drawing, dated June 20, 1852, I find that this discovery 

 was made simultaneously with Hofmeister's.) — Zur Entwick. d. Equiseteen 

 Bot. Zeitung, Aug. 6, 1852, p. 53/. 



II Ueb. Keimung der Equisetaceen. Flora, 1852 (June 7), p. 385. — 

 Beitr. z. Kenntn. der Gef ass-Krjrptog. Abhandl. Sachsisch. Gesellsch. der 

 Wissensch. Leipsic, 1852, p. 168. pi. 17-19. 



^ B. Bischofi" describes an exceptional case in Eq. sylvaticum, L. (Be- 

 merk. z. Entwick. der Equiset. Bot. Zeit. 1853, p. 97.) 



** Vide Milde, Nova Acta A. C. L. C. xxiv. pt. 1. pp. 68, 71 (1854). 



W Vide Hofmeister, op. supra cit. 



XX Milde yras fortunate enough ta press out this cell * entire' from a 



