18S Dr. Schleiden on the Development of the 



branous fold gradually covers in the nucleus, (Integumentum 

 jyrimum aut internum mihi ; Secondine Mirb. ; memhrana in- 

 terna auct.) Sometimes soon after, and indeed almost contem- 

 poraneously with this, sometimes later*; sometimes immediate- 

 ly below the first protuberance, at other times at some distance 

 from it (as for instance in many PolygonecE and Cistinece)^ we 

 may next observe a second protuberance, which, as the second 

 integumentf, covers in the first. {Integumentum secundum 

 sive externum mihi ; Primine Mirb. ,♦ Testa auct.) The first- 

 formed integument certainly does frequently consist only of a 

 fold of the epidermis of the 7iucleus; nevertheless we do find 

 a tolerably thick parenchyma taking part in its formation in 

 almost all those families which form no second integument, 

 and also in some which possess both coverings, as, for instance, 

 in the Euphorbia ceco, Cistinecn, and Thymelece. In the case of 

 these three families, a peculiar process takes place, namely, 

 upon the seed becoming ripe the external integument is gra- 

 duall}' absorbed, until nothing but a thin membrane is left, 

 usually described as epidermis testce, or in the Euphorbiacece 

 it has been given as arillus ; and on the other hand, the actual 

 modified epidermis testcc has also been described as the aril- 

 lus^ for instance, in the Oxalidece, The apex of the original 

 papilla, which develops itself as nucleus, varies exceedingly 

 in its size in proportion to the entire ovule, if examined in the 

 different families. It often forms a long and nearly cylindri- 

 cal body, as in Loasa and Pedicularis\ in many cases it is 

 shorter, so that that portion of the ovule in which no distinction 

 has taken place between nucleus and integument (the whole 

 being like a fleshy distended stalk), is by far the more predo- 

 minant, as in all the Synantherece^ Canna^ Phlox^ Polemomium : 

 it consists again, in some instances, merely of the extreme point 

 of the papilla itself, as in Convolimlus ; or nothing more than 

 an ideal point remains, which can no longer be distinguished 

 as an independent body, above which, however, a protube- 

 rance develops itself, and thus forms a micropyle, as in the 

 Dipsacece, 



Of course the process I have been describing becomes con- 

 siderably modified in individual points, either through the uni- 

 lateral development of the o\\\[e{ovulum campylotropum Mirb.), 



* This is most conspicuous in Taxus, in which the second integument 

 (fig. 1 b.) does not exist until after impregnation has taken place {cupula 

 auct). 



t I observed this to occur very distinctly in Hydrocharis and Val- 

 lisneria ; and, as Richard's analysis shows, all other true Hydrocharidecs 

 have atropous ovules. Endlicher's attribution of an anatropous ovule to 

 this family {Genera Plantarum^ p. 160) is probably derived from a partial in- 

 vestigation of Stratiotes (which perhaps does not belong here), and which 

 has been extended to the remainder of this family. 



