118 REPORT — 1851. 



" After the ripe spores have lain a longer or shorter time in water, a process 

 of cell-formation commences at that point of the spore, within the proper, 

 internal spore-cell, whence results the formation of a cellular body occupying 

 only a small portion of the internal cavity of the spore. The cells multiply 

 rapidly, and break through the exine, appearing externally as the green cellu- 

 lar papilla called the ' keim-nmlst' by Bischoft', the 'papilla of the nucleus' 

 by Schleiden. I see no ground why this should be named otherwise than as 

 the fro-embryo. In Pilularia it is very soon seen, where the pro-embryo 

 consists of only about thirty cells, completely enveloped by the exine, and 

 where the only external evidence of its existence is a little protuberance, — 

 that the pro-embryo consists of a large central cell surrounded by a simple 

 layer of smaller ones. The smaller cells covering the apex of this large cell, 

 four in number, elongate into a papilla before the pro-embryo bursts through 

 the exine, which splits regularly into twelve to sixteen teeth ; — subsequently 

 they become divided by horizontal walls, and then appear as the organ which 

 Schleiden, and after him Mettenius, supposed to be ' pollen-tubes ' produced 

 from some of the small spores. These papilliform cells most certainly ori- 

 ginate from the pro-embryo, a fact which takes away all material ground 

 from Schleiden's theory. 



" The four papilliform cells separate from each other and leave a passage 

 leading to the large central cell. In this cell the young plant originates 

 shortly after the smaller spores, which never produce ' pollen-tubes,' begin 

 to emit the cellules containing spiral filaments discovered by Nageli. I ob- 

 served and dissected out an embryo consisting of only four cells. It com- 

 pletely filled the large central cell, and there was not the least trace of a 

 pollen-tube attached to it. 



" The organization of Salvinia is somewhat different from this. On every 

 pro-embryo several, as many as eight cells of the outer surface of the cellular 

 layer next but two to the obtuse triangular cellular body, acquire a consi- 

 derable size, a spherical form, and become filled with protoplasm ; the four 

 cells covering each of these larger cells lose the greater part of their chloro- 

 phyll and separate from each other to leave a passage leading down to the 

 large central cell. In this large cell the young plant originates. The number of 

 these organs inSalvinia allows the possibility of the occurrence of poly-embry- 

 ony in this genus ; I observed two embryos on one pro-embryo in one case. 



" It is out of the question to talk of a ' larger pollen-tube' in Salvinia. 

 Mettenius has already shown that the structure of the small spores renders 

 such a product from them impossible." 



Dr. Mettenius's Essay on the Vascular Cryptogams*, already frequently 

 referred to, confirms the preceding account in all essential points, some slight 

 criticisms relating only to the structure of the coats of the spore ; and it adds 

 a description of the development of the *' ovules " in the pro-erabryo of 

 Marsilea Fabri, which agrees closely with that in Pilularia. Hofmeister-j* 

 has recently announced the discovery of the production of cellules contain- 

 ing spiral filaments from the small spores in Salvinia, ']\x&t as Nageli saw thera 

 in Pilularia. 



General Conclusions. 



In the facts of which I have given confessedly a very imperfect resumi in 

 the preceding pages, we have two important points to consider. In the first 

 place, we have to determine how far they suffice to warrant the belief in the 



* Beitrage zur Botanik. Heidelberg, 1850. 



t Flora, 1850. p. 700 (in a note to a review of Mercklin's Essay on the Reproduction of 

 Ferns). 



