150 APPENDIX ON PRACTICAL WORK. 



the oldest flowers are in the above position (fig. 35), the inflorescence is 

 centrifugal, definite, or cymose. 



VII. The Flower :— 



2. Receptacle. — Cut through the flower longitudinally, and determine 

 whether the flower is hypogynous, perigynous, or epigynous (fig. 37). 

 The receptacle is often very much shallower than in B ; as, for example, 

 in gorse and sweet-pea. 



3. Relation of Parts, as shown in a floral diagram. Take fig. 38 as 

 a model. Note position of axis, denoting back of flower. In a bila- 

 terally symmetrical flower, rising, like a pansy, from a condensed stem, 

 the back is above and the front below. A flower may be more or less 

 twisted round, especially in orchids (p. 89). 



Note carefully whether there is an anterior or posterior sepal (p. 82). 

 Make a good-sized drawing (say three times as big as fig. 38), and do not 

 crowd the stamens and carpels. When these last are numerous, as in 

 buttercup, do not trouble to count them, but put a fair number of the 

 conventional marks. 



It is very useful practice to pin out the parts in the form of a dia- 

 gram, marking with pencil the front, back, and planes (fig. 38). If 

 the calyx or corolla has its elements cohering, cut it into longitudinal 

 pieces between the lobes or teeth, and lay them out as if originally 

 separate. 



A floral formula can be made to express a great deal. Thus the 

 diagram in fig. 38 can by represented by 



Ca 3, Co 3, An 3 + 3, Gn & 



Ca. = calyx ; Co. = corolla ; An. = andrcecium ; Gn. = gyncecium. 

 A parenthesis ( ) signifies cohering parts. In the case of the gyncecium, 

 a line below means superior, a line above inferior. Superposition be- 

 tween the whorls is indicated by |. Thus, in primrose : — 



Ca (5), Co (5) I An 5, Gn », 



or I can be omitted if An o + 5 is inserted. 



Other typical formulae are : — 



Buttercup : — 



Ca 5, Co 5, An ~, Gn 90 c«. 

 (Here rv> = spirally arranged.) 



Carrot : — 

 Orchis : — 

 Most Grasses 



Ca 5, Co 5, An 5 + o, Gn fa}. 

 Ca 3, Co 3, An 1 + o, Gn pj. 



Ca o, Co 2, An 3 + 0, Gn !9. 

 The o signifies suppression of a whorl. 



( For arrangement in bud, see footnotes pp. 49 and 84. 



4. Calyx. — } See also iv. 2. Remaining terms in footnotes : open, 



5. Corolla.— } petals of mignonette ; valvate, sepals of fuchsia ; obvo- 



[ lute, petals of fuchsia; crumpled, petals of poppy. 



