ANGIOSPERMS. 



413 



species, and is constant within larger or smaller cycles of affinity. If the whorls of a flower 

 have each the same number of members, and are so placed that the members of the dif- 

 ferent whorls stand over one another, forming orthostichies, they are said by Sachs and 

 Payer to be superposed (the usual term is ' opposite ') ; if the stamens are superposed on 

 the calyx or corolla they are said to be antisepalous or antipetalous ; if the members of 

 a whorl lie between the median planes of the members of the whorl next above or 

 below, the whorls alternate, and Braun terms flowers in which all the whorls have the 

 same number of members and alternate eucycHc. But it sometimes happens that new and 

 similar members are subsequently developed between the members of a whorl already 

 fortned, as for instance five later stamens between the five first formed in Dictamnits 

 Fraxinella (Fig. 305 C), and probably in many eucyclic flowers with ten stamens ; 

 members thus subsequently introduced into a whorl may be termed t?tterposed. (For 

 further remarks on this subject see below.) 



The consideration of the number of the parts of the flower is necessarily connected 

 with that of their relative positions ; but before we enter more at length into this point 

 it will be well to explain the diagram of a flower. 



The floral diagram is constructed in various ways according to the purpose which 

 it is intended to serve. It is sometimes treated as a free drawing of an actual transverse 

 section, and not only the number and position but approximatively also the form, 

 cohesion, size, etc. of the parts of the flower are given in it ; the purpose here intended 

 is however best attained by preparing accurate drawings of actual transverse sections 



of flower-buds, which will then indeed contain much that for certain purposes is 

 superfluous. But if the object is merely to show the number and position of the parts 

 of the flower in such a manner as to make the comparison of a number of flowers in 

 these respects as easy as possible, the best plan is to disregard all other considerations 

 and to frame all diagrams upon one and that the simplest plan, so as to show only the 

 relative numbers and positions of the parts in all their variations. The diagrams given 

 below have exclusively this object in view, and Figs. 340 — 342 are examples of them. 

 They are horizontal projections, the floral axis being supposed to be vertical. The 

 transverse sections of the axis which bear the foliar structures, the sepaline, petaline, 

 staminal and carpellary leaves, are drawn as concentric circles, on which the separate 

 structures are inserted. The development being acropetal the outermost circle is the 

 oldest and in many cases also the lowest. The dot above the diagram always indicates 

 the position of the mother-axis of the flower, and therefore the lower part of the 

 diagram is anterior. Though simple dots are quite sufficient to indicate the number 

 and position of the parts of the flower, different signs have been chosen for the different 

 foliar structures, to enable the eye quickly to catch the ineaning of the diagram ; the 

 leaves of the perianth are represented by segments of a circle, those of the outer circle 

 or calyx having an appearance of a mid-rib, that they may be distinguished at first sight 

 from the leaves of the inner circle ; the sign chosen for the stamens is like the transverse 

 section of an anther, but there is no attempt to indicate the position of the pollen-sacs 

 or of their dehiscence, whether inward or outward ; the branching of the stamens is 

 expressed by placing the signs in groups, as in Fig. 342, where the five groups answer 



