864 VARIOUS PLANT GROUPS 



peach (Fig. 94, page 80), plum (Fig. 95, page 90), clierry 

 (Fig. 96, page 90), raspberry (Fig. 97, page 91), straw- 

 ))erry (Figs. 98 I-III, i)age 92), and roses (Figs. 148 II, 

 III, 298, pages 150, 151, 378), is seen to possess many 

 features of floral structure resembling more nearlj^ those of 

 the crowfoot family than of any other family we have 

 studied. 



Note in the formulas of Rosa, Fragaria, Rubus, Prunus, Cydonia, 

 and PjTUS, given on jiages 408, 409, that the floral envelopes are 

 mostly in fives, while the essential organs are commonly numerous, 

 and that all are free anfl distinct, except sometimes the carpels, 

 which then, unlike ])oi)py carpels, have axilc placenta'. 



An unusual form of calyx is found in strawberries (Fra- 

 garia). Here the sepals have stipules which coalesce in pairs so 

 as to form what looks like a calyx upon a calyx, and is termed 

 therefore an cplcalyx.^ The only other features not before 

 encountered belong to the torus and the fruit. Throughout 

 the family the torus is concave or cup-like, and it is mostly 

 free as in peonies and our examples of the laurel family. In 

 roses (Rosa) it complelily envelopes the carpels, and be- 

 comes fleshy and l)right colored while the pericarps ripen 

 into hard nutlets,- the whole forming a so-called "hip." The 

 strawberry fruit consists mainlv of the u])i:)er ])art of the 

 torus,- much swollen and bearing numerous achenes. Rasp- 

 berries have the uppei- part of the torus comjjaratively dry, 

 and in fruit th(^ pericarps finally separate from it. As these 

 ripen, an outer layer becomes fleshy wliih^ an inner layer 

 hardens like an olive stone. A fruit in which th(> ]>ericarp 

 is thus differeniiated is called a "stone-fruit " or tlrypc^ In 

 raspberries and tliimblel)ei-ri(>s the little dru])es coalesce 

 sufficiently to form a thimble-like ma.ss after they separate 

 from th(> torus. In blackberries, on the contrary, the little 

 drupes remain atta(4ied to the part of the torus which bears 



' E"pi-ca'lyx < 1j. r/)/, upon. S| 



2 The hardening of the pericarp is cxpressiHl in the formulas by two 

 inverted exclamation marks. 



■' A small t to represent ])art of Ihe tonis is used in the formulas instead 

 of the large capital. 



' Drupe < L. drvpn, a ripe olive. ('//.' 



