1 102 A TEXTBOOK OF THEORETICAL BOTANY 



and petals are usually symbolized by conventional crescent-shaped outlines; 

 stamens may also be symbolized by points or by outlines of the anthers in 

 cross-section. The gynoecium is represented by a cross-section of the 

 ovary. The positions of bract, bracteoles and axis are usually indicated out- 

 side the flower and accessory structures inside it, such as nectaries, may 

 also be indicated. In the plan of the perianth account must be taken of the 

 relative sizes of the members, and of course, of any departure from normal 

 equidistance in any region. Similarly the spiral or cyclic sequence must be 

 shown, and the cohesion or adhesion of members is indicated by lines of 

 linkage drawn between them. Irregularities should also be shown, such as 

 the presence of a petal or sepal spur, which is indicated by a loop attached 

 to the back of the appropriate symbol. Lastly it may sometimes be desirable 

 in special cases to mark with a cross or a dotted line the positions of lost or 

 abortive members. 



A floral diagram thus constructed is an abstraction, in so far as it omits 

 all the small details which make up the specific personality of a flower. It is a 

 generalization which, in many cases, holds good for an entire genus or even 

 for a number of genera in a family and it is, finally, an interpretation, in 

 obscure cases, of the morphological conclusions of its author. 



Alongside the floral diagram we must rank the floral formula, which 

 we owe to Grisebach. In this we summarize the numbers of the parts, under 

 the initial letters: K (Calyx), C (Corolla), A (Androecium) and G (Gynoe- 

 cium). P (Perianth) may be used where there is no distinction of calyx and 

 corolla. Each initial is followed by the number of the respective organs, 

 placed between brackets if they are coherent, and divided between their 

 respective whorls if more than one whorl of any given member is present. 

 If the number of parts is large and variable the sign a is used instead of a 

 number. Thus: 



The symbol B, if added, indicates actinomorphy, and i- indicates zygo- 

 morphy. The lines above or below the figure for the gynoecium indicate 

 an inferior or superior ovary, respectively. If two distinct sets of parts are 

 adherent, the figures for the two sets may be enclosed in square brackets. 



A flower in which the number of parts in each whorl is the same through- 

 out the flower is called isomeric, as for example in certain species of 

 Sedum in which the floral formula is K5 C5 A5 G5 or in Liliaceae, 

 P3+3 A3 +3 G3. The opposite condition, where there are unequal num- 

 bers, is called heteromeric or heterocyclic, e.g., Nicotiana, K5 C5 A5 G2. 



The vertical symmetry of the flower, that is the relation of its parts as 

 seen in vertical, median section, varies according to the position of the 

 gynoecium in relation to the other parts. In the majority of flowers the 

 receptacle is either conical or spheroidal in shape, and the order of parts 



