PLAN-DIAGRAMS 



[CH. 



plan -diagrams of buds of Rhamnus and Elm respectively, 

 a certain proportion of theory is expressed in the diagrams, 

 by the insertion of a conventional sign indicating the 



Fig. 28. 



Fig. 29. 



Fig. 28. Plan-diagram of a bud of Rhamnus catharticus with the 

 outer bud- scales opposite, gradually passing inwards to obvious pairs of 

 stipules overlapping at the edges, the innermost with their accompanying, 

 opposite, involute leaves. 



Fig. 29. Plan-diagram of a bud of Elm, the outermost (stipular) bud- 

 scales distichous and overlapping at the edges, gradually passing to pairs 

 of stipules with their leaves. The latter distichous, and conduplicate 

 with the margins directed towards the axis of the. shoot. 



position of the axis, and of a leaf of the axis, at a and c 

 respectively, showing the position of the leaf in the axil of 

 which the bud was developed. 



This leads us then to the distinction between a mere 

 diagram of a transverse section of the bud and a plan- 

 diagram in which is indicated more than can be seen in a 

 section at any one level. In the preparation of the latter 

 it may be necessary not only to examine sections at various 

 levels, but also to introduce features not actually existing 

 e.g. the hypothetical leaves which would be found in 

 the positions of the numbers between the stipular scales 



