402 11EDUCTION TO A NUCLEUS. [BOOK i. 



have crept into the preceding enumeration (perhaps in 

 Delphinium) . But even if it is only correct in the main, the 

 conclusion is inevitable that the number of ovular integu- 

 ments, though constant in most other families, is among 

 Crowfoots, a variable and consequently secondary character, 

 by means of which alone the natural order cannot be limited. 

 He finds similar anomalies among Arads, where there is 

 nothing constant in the formation of the ovule, except the 

 double integument of all monocotyledons. (See Annals of 

 Natural History, v. 165.) 



The reduction of the ovule to a mere nucleus has been 

 treated of by Mr. Griffith, in his memoir on the ovule of 

 Santalum, &c.: 



" The non-development of either of the ordinary integu- 

 ments of the ovulum, that is, the reduction of this to the 

 nucleus, was, so far as I know, first observed by M. Adolphe 

 Brongniart in Thesium ; and this is the only point on which 

 the observations of that distinguished botanist agree with the 

 later ones of M. Decaisne. This sort of reduction or sup- 

 pression is now known not to be uncommon ; it is usually, I 

 believe, considered to be limited to antitropal ovula; but 

 from the consideration of Galium, Callipeltis and Osyris, I am 

 inclined to believe that changes in direction affect nucleary 

 ovula similar to those affecting more complete ovula, so per- 

 manently established by M. Mirbel. This suppression having 

 first been made manifest in Santalacese, it naturally became 

 a subject of consideration whether it did not exist in similar 

 placentatioiis of certain other natural families, of which 

 Olacinese, certain Verbenacese and Avicennia are marked 

 examples. On this subject ray direct observations are con- 

 fined to Congea ; and although these are incomplete, I am 

 led to believe that there is not any connexion between this 

 mode of placentation and this mode of suppression. It is 

 curious, however, that the ovula of the above instances, so 

 far as I am acquainted with them, simulate at the period of 

 expansion of the flower in a sufficiently marked manner the 

 ovula of Santalaceae." (Linncean Transactions, xix. 185.) 



The reduction of the ovule to little more than an amniotic 

 sac was remarked by the same great observer who showed 



