60 



THE PERIGONE 



rolled inward, the Involute form. When lapping the one over the 

 other they are Imbricate (Fig. 123, the corolla). Here it is important 

 to note whether the overlapping is from right to left. Dextrorse (Fig. 

 125), or the reverse, Sinistrorse (Fig. 124). In determining this point, 

 the relations can best be understood by imagining the flower as a man, 

 his feet in the direction of the torus and his hands representing the 

 petals. To be dextrorse, his right hand must be covered by his left. 

 In other words, the terms "right" and "left," in this position, signify 

 right-covered and left-covered, not right-covering and left-covering. 



/ZJ. /2& 



Fig. 120. Bud of I-pomoea with open calyx and convolute corolla. 121. Transverse section through 

 valvate reduplicate calyx of Hibiscus. Fig. 122. The same, valvate-induplicate calyx of Clematis. 

 124. Sinistrorse imbrication of " corolla-lobes of Lochnera. 125. Dextrorse imbrication of corolla- 

 lobea of Eckiles. 



Petals, sepals, or stamens are occasionally rolled vertically down- 

 ward from the apex, this form being called Circinate. Occasionally we 

 find the petals folded and doubled in an irregular manner, the Crumpled 

 or Corrugated form of praefloration. A number of terms are called for 

 by the peculiar conditions of the gamopetalous form. Economy of 

 space is here commonly secured by longitudinal folding, the Plaited 

 form. Vertical shortening is often secured by t'wisting, the Convolute 

 form (Fig. 120, the corolla). In this case it is important to determine 

 the direction of the contortion as dextrorse or sinistrorse, in the same 

 way as that of imbrication. 



Other details as to the precise mode of overlapping are frequently 

 worthy of note. 



In determining the form of praefloration, care must be taken to 

 select a well-formed bud. 



The Mixed Form. — The praefloration may be mixed, as in Oenothera, 

 where the parts are valvate at the base and slightly imbricate or redu- 

 plicate at the immature apex. At the best, intermediate and perplexing 

 forms will be encountered. 



