T.KS3ON 30.J HOW TO STUDY PLANTS. 183 



family. The families are so numerous, and so generally distinguish- 

 able inly by a combination of a considerable number of marks that 

 the student must find his way to them by means of a contrivance 

 called an Analytical Key. This Key begins on p. 12. 



527. It takes note of the most comprehensive possible division of 

 plants, namely those " producing true flowers and seeds," and those 

 " not producing flowers, propagated by spores." To the first of 

 these, the great series of PH.ENOGAMOUS or FLOWERING PLANTS^, 

 the plant under examination obviously belongs. 



528. This series divides into those " with wood in a circle, or in 

 concentric annual circles or layers around a central pith, netted-veined 

 leaves, and parts of the flower mostly in fives or fours," to which 

 might be added the dicotyledonous embryo, but that in the present 

 case is beyond the young student's powers, even if the fruit were at 

 hand ; and into those " with wood in separate threads scattered 

 through the diameter of the stem, not in a circle," also the "leaves 

 mostly parallel-veined, and parts of the flower almost always in 

 threes, never in fives." Although the hollowness of the stem of the 

 present plant may obscure its internal structure, a practised hand, 

 by throwing the light through a thin cross section of the stem under 

 the glass, would make it evident that its woody bundles were all in 

 a circle near the circumference, yet this could hardly be expected 

 of an unassisted and inexperienced beginner. But the two other 

 and very obvious marks, the netted-veined leaves, and the number 

 five in both calyx and corolla, certify at once that the plant belongs 

 to the first class, EXOGENOUS or DICOTYLEDONOUS PLANTS. 



529. We should now look at the flower more particularly, so 

 as to make out its general 



plan of structure, which we 



shall need to know all about 



as we go on. We observe 



that it has a calyx of 5 



sepals, though these are apt 



to fall soon after the blossom 



opens ; that the 5 petals are ss 



borne on the receptacle (or common axis of the flower) just above 



the sepals and alternate with them ; that there are next borne, a 



FIG. 358. A flower of a Buttercup (Ranunculus bulbosus) cut through from top to bottom, 

 and enlarged. 



