CENTAUREA AMERICANA. AMERICAN CENTAUREA. 7 I 



features, as well as for its native beauty, and its easy adaptation 

 to orarden culture. As the student knows, the bracts which q-q to 

 make up the involucral scales in this natural order, and which in 

 this CeutauTca have a pretty comb-like appearance, are but 

 leaves which have been suddenly and nearly suppressed. The 

 whole head of flowers is indeed a long stem which has been 

 drawn into a small compass, as would be a wire spring pressed 

 down. One phase of stem growth ceases when the flower begins 

 to form. The flower is indeed the effort of a second growth- 

 wave, and, instead of the leaves winding round the branch as in 

 the first wave of growth, the changed leaves and axillary buds as 

 scales and fiowers, wind round the receptacle. Now in view of 

 this morphological law we might expect the numerical parts in 

 the second wave to accord somewhat with the first, — that is to 

 say, a plant with leafy stem should have a great number of 

 involucral scales or other floral parts. We do not always see 

 this correspondence, because the parts will often be wholly 

 absorbed, united with each other, or suppressed ; but we often 

 may, and it is especially to be seen in the case of the American 

 Centaurea, which has a very leafy stem, and a correspondingly 

 numerously-bracted involucre. Again, the pectinate, or comb- 

 like appendage to the scale, is interesting as showing a power in 

 the genus to have pinnately parted leaves. There is nothing 

 else to indicate this power in this particular species, for the 

 leaves are remarkably entire; that is, showing no indications of 

 any lobes or parting along the edges. But on seeing these pin- 

 natifid bracts, and knowing what we now know of their typically 

 leafy character, a student meeting this species for the first time 

 he ever saw one of the genus, might fairly expect to find pin- 

 nately parted leaves in some of them. And this he really 

 may do, for there are other species with such divided leaves. 

 The much swollen upper portion of the hollow stem is extremely 

 interesting. The numerous grooves in this portion give some 

 indication of the great numbers of primordial leaves which have 

 gone to make up this huge compound flower. The normal 



