935 



forcible tearing of the spiral filaments to which I have just alluded. 

 The embryonary globule is produced by the union of the germinal 

 vesicle with the embryo, and it is only attached below to the base of 

 the cavity containing the embryo-sac by a very delicate filiform em- 

 bryo-support. The colourless nuclear papilla dies away and dries up 

 as the embryonary globule grows, and the canal assumes a brown co- 

 lour. In this state it continues for a long time upon the now expand- 

 ing cavity of the nucleus. Usually only one of the numerous naked 

 ovules formed upon the pro-embryo developes its embryo. This 

 does not appear extraordinary, since similar examples are not wanting 

 in the vegetable world, and in many palms one only of the three 

 original compartments is perfectly formed. An especial cause may 

 be sought for here in the small size of the pro-embryo, w r hich does 

 not supply sufficient nourishment for several embryos. With the 

 further development of one embryo, the others (the other rudimentary 

 ovules) die. In these the mouth of the papilla of the nucleus opens, 

 and allows the dead spiral filaments and the rest of the contents to 

 escape. The canal, and especially the cavity for the embryo-sac, 

 then exhibits a brown colour. In this state the latter may be most 

 distinctly recognized. On the contrary, this part in vegetating ovules 

 can only be observed by a most careful extract of the single organ. 

 For while on the one hand it is covered by the still erect nuclear pa- 

 pilla, the want on the other hand of any peculiar colour, or of other- 

 wise distinguishing outlines, renders the detection of it impossible. 

 Polypodium aureum is, next to Pteris serrulata, the best adapted of 

 all the species which I have examined. The impregnation of all the 

 families, genera and species is just according to the above-described 

 type ; an exception occurs in the appearance on the border of the 

 pro-embryo, even in its earliest stage, of a spiral filament-organ, dif- 

 fering somewhat in structure as it loses its uni-cellular aspect. Five 

 or six parietal cells are formed, which enclose in the middle a space 

 either filled with spiral filament-cells or hollow spaces. These struc- 

 tures must be regarded as monstrosities of the spiral filament-organs, 

 since they only occur in diseased conditions, and in individuals which 

 never produce an embryo. Such a barren pro-embryo either decays 

 soon after its origin, or, passing into a succulent state of growth, ap- 

 pears much larger than is natural. In this state it resembles a Mar- 

 chojitia, and usually produces a great number of abortive ovules." 



Almost immediately after the entrance of the spiral filament into 

 the canal of the pistillidium, and its supposed contact with the ovule 



