1899.] NATURAL SCIENCES OF PHILADELPHIA. 87 



should furnish a good foundation for subsequent investigation. 

 Taking a fairly vigorous branch of Clethra alnifolia, we note that 

 the phyllotaxis is on the f plan. AYe may, on this fact, look for 

 a pentamerous system to prevail in the subsequent development, 

 and charge to consolidation or to abortion any variation from this 

 type. Following again the Clethra, we find a five-cleft calyx, and 

 we say it is normal. Then we have five petals alternate with the 

 sepals, which again we j^ronounce normal. But the next cycle 

 appears as ten stamens, which for a single cycle would be out of 

 order. Observing closely, however, we note that five of the ten 

 are longer than the others, and we learn that there are really two 

 cycles of five, of which the long stamens represent the outer. 



Taking up now the gynojcium : the stigma is noted as being 

 .slightly three-cleft, indicating a tricarpellary ovarium. There should 

 be five. Two are wanting. This sudden departure from what 

 has hitherto been a regular pentamerous series, suggests that there 

 has been a suppression of several verticils since the appearance of 

 the last staminal whorl. A glandular disk fills the intei-space, and 

 we may reasonably conclude that herein lie the missing links. The 

 carpellury system here is parallel to prolificacy as often seen in 

 flowers. One rose proceeds from the centre of another rose, or a 

 small orange at the apex of a larger one, as in the variety known 

 as the navel. The upper one, as in the case of the gyn«cium of 

 Clethra, loses mnch of the normal vitality of the individual. 



In some genera of Ericaceje cohesion — vital power in its higher 

 stage — lilajs a part in organizing, the reverse of the lower degree, 

 but still with the same result in the disappearance of parts that 

 me may term primarily separate. In examining a large number of 

 Clethra flowers, a pair of stamens will occasionally be found as 

 completely consolidated into a single filament as the carpels have 

 had the three styles united; the extreme upper portions of each, 

 however, continuing normal. It shows a tendency to consolidation. 

 From a consideration of all the facts, we may conclude that the 

 primary type of Ericaceae is pentamerous and polypetalous, that 

 those approaching this type are the oldest in the genealogical line, 

 and that all the variations from this type in the order are deduci- 

 ble from the variations in growth-energy resulting in the abortion 

 or consolidation of primary parts. 



