216 



PRINCIPLES OF PLANT-TERATOLOGY. 



three cotyledons all of equal size and symmetrically 

 grouped to form a whorl of three (PI. XXII, fig. Id) ; 

 in another there were four equal cotyledons, and these 

 were grouped as shown in the figure, the two resulting 

 halves of each divided cotyledon turning through an 

 angle of 90° and coming to lie almost opposite to each 

 other (PI. XXII, fig, 1/). In another seedling one 

 cotyledon only had divided, the two resulting members 

 being" each of them much smaller than the undivided 

 cotyledon (PL XXII, fig. 1c). Yet another case was 

 similar to the last except that the division into two 

 cotyledons was not quite completed, the two organs 

 being still united below ; but their free laminse were 

 directly opposed to each other, as are the two cotyle- 

 dons in a normal seedling (PI. XXII, fig. la and b). 

 The normal counterpart of the abnormal phenomenon 

 just described is seen in the seedlings of some Gymno- 

 sperms, e. <j. the pine, in which congenital division of 

 the cotyledons into as many as fifteen occurs. This 

 formation of the cotyledons in the pine seems to be quite 

 analogous to that of the four embryos in the same plant. 



Although the cotyledons may increase in number, so 

 that the two opposite ones maybe replaced by a whorl 

 of three or four, no cases appear to be known of these 

 organs changing their position in the vertical direction. 



Forking and multiplication of the cotyledon is 

 apparently unheard of in Monocotyledons. 



Foliage Leaves. 



1. Lateral. — a. From Opposite-decussate to Whorled, 

 — A change in the leaf-arrangement is most commonly 

 met with in plants which have opposite-decussate 

 leaves. In these we have to denote two distinct types 

 of change. In the one case the pair of opposite leaves 

 may become changed into a whorl of three or four, 

 and this takes place by apical fission of one or both 

 of the leaves concerned ; and transitional cases occur 

 in which one or both of the leaves is more or less 



