FISSION OF LEAVES. 66 



glabra wherein the blade of the leaf on pne side was 

 deeply and irregularly laciniated, the ot'her side re- 

 maining entire. (Verhandl., d. 35, Naturvorschef- 

 versamlung, tab. 3.) Laciniate varieties of plants are 

 of frequent occurrence in gardens where they are often 

 cultivated for their beauty or singularity ; thus, there 

 are laciniated alders, fern-leaved beeches and limes, 

 oak-leaved laburnums, &c. A list of several of these 

 is subjoined. A similar fission takes place constantly 

 in the cotyledons of some plants, sometimes, as in 

 Coniferce, to such an extent as to give an appearance 

 as if there were several cotyledons.^ 



It is not always easy to recognise, at a first glance, 

 whether the division be the result of disunion or of an 

 incomplete union of two leaves, but we may be guided 

 by the number of leaves in the cycle or the whorl. 

 The number is complete in cases of partial disjunction, 

 while in cases of fusion it is incomplete. Again, in in- 

 stances of disjunction, there is only one point of origin, 

 but, when two leaves are grafted together, two such 

 points may generally be detected at the base of the 

 leaf, or a transverse section of the leafstalk will show 

 indications of fusion. The number and position of the 

 midribs will also serve as a guide, as in cases of fusion 

 there are generally two or more midribs, according to 

 the number of fused leaves ; but as Moquin well remarks, 

 this latter character cannot be always depended upon, 

 for the median nerve may divide without any corre- 

 sponding separation of the cellular portions of the leaf. 

 The author just quoted cites examples of this kind in 

 Cardamine pratensis, Hedera Helix, Plantago majors 

 Geranium nodosum. 



The following list of plants commonly producing 

 leaves that are cleft or divided, to a greater extent than 

 is usual in the species, is mainly taken from one 

 given by Schlechtendal, ' Bot. Zeit.,' 1844, p. 441, 

 with additions from other sources. The ! indicates 

 that the author has himself met with the deviation in 



Duchartre, ' Ann. Sc. Nat.,' 3rd serios, 18t8, vol. x, p. 207. 



5 



