STRUCTURE.] NUMBER OF INTEGUMENTS. 401 



Gasparrini also states, that in the seeds of the common 

 China Orange (Citrus Bigaradia sinensis) there are several 

 embryos, which are different from each other both in form 

 and situation. Usually their radicle is turned to the fora- 

 men, sometimes it is entangled in the sides of the inner skin, 

 and occasionally, but rarely, embryos are to be found with 

 the radicle turned to the chalaza. This very curious and 

 unexpected observation I have not been able to verify. 



Besides the two external integuments, Mirbel remarked 

 the occasional presence of three others peculiar to the nucleus, 

 which he calls the tercine, quartine, and quintine. These 

 terms are now, however, disused, and arose from imperfect 

 observations. The tercine was the surface of the nucleus ; 

 the quartine a layer of tissue belonging to the tercine, and 

 the quintine what is now called the sac of the amnios. 



Recent investigations show that the number of integu- 

 ments or sacs found on ovules never exceeds two, is frequently 

 only one, that not uncommonly the nucleus is naked, and 

 that there are even examples of an ovule consisting of no 

 more than an amniotic sac. 



It has been stated by Fritzche in Wiegmann's Archiv., 

 that, in many plants, the ovule has but one integument, as in 

 Conifers, Composites, Lobeliads, Gentianworts, &c. ; and in 

 others two, as in Buckwheats, Rockroses (Cistacese), Urticals, 

 Arads, and all other endogens, &c. He moreover found that 

 while all endogens have two integuments of the ovule, the 

 majority of monopetalous exogens have but one, whilst the 

 polypetalous usually possess two. 



Schleiden has, however, shown that the number of integu- 

 ments of the ovule, varies in Crowfoots (Ranunculacese), even 

 in the same genus. There is but one integument in Thalic- 

 trum, Anemone, Ranunculus, Caltha, Helleborus, some Del- 

 phiniums, and Podophyllum. Two integuments, he says, 

 occur in Clematis, Adonis, Trollius, Isopyrum, Aquilegia, 

 Aconitum, Paeonia, several Delphiniums, and also among 

 Magnoliads. So great, he adds, is the difficulty of examin- 

 ing most plants of this family with reference to the original 

 structure of their ovule, that possibly some error may 



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