1893.] NATURAL SCIENCES OF PHILADELPHIA. 293 



sionally, especially in the Larch where the tree is young and in a 

 very vigorous condition, the growth-wave not being wholly 

 exhausted, will make another venture, and a weak shoot from the 

 apex of the cone results. In Rosacea? the same phenomena are by 

 no means uncommon. One rose blossom will push out from the 

 center of another, and a small branch bearing a miniature pear has 

 been known to spring from the crown of a pear of normal char- 

 acter beneath it. 



The main purpose of this paper is to note the remarkable origin 

 of the variety of orange known as the Tangerine, and this by rea- 

 son of a singular variation in the character of the force in the 

 rhythmic wave. In the primary wave, for some reason yet obscure, 

 it is remarkably weak, and sends the greater part of its effort into the 

 secondary one. What is usually the small orange within the larger 

 in the double orange, or the minute orange in the apex of the navel 

 variety, becomes the leading and only original fruit ! 



Once in a while nature furnishes the absolute proof of this mor- 

 phological conception. It is not rare to have specimens of Tanger- 

 ines in which are from five to ten abortive carpels at the base 

 of the fruit. In these cases the well defined axis, usual in the com- 

 mon orange, runs through the lower abortion, to be suddenly and 

 finally suppressed when the upper cycle of organs takes its turn to 

 become fruit. The Tangerine has always a flattish or oblate form. 

 The utter suppression of the axis at the point of its formation nat- 

 urally favoring a lateral growth. 



The key herewith furnished, will doubtless disclose to us the 

 secret of the many forms which the citrus tribe often assumes. The 

 length of the lemon as compared with the more globular orange is 

 evidently due to a more rapid advance of the growth wave. This 

 naturally leads to a more elongated form. This hypothesis is sup- 

 ported by examining a half section of the lemon taken longitudi- 

 nally. The axis is much more apparent and more woody than in the 

 orange. It will be found to have come to a rest at the apex of the 

 oval, starting again as from a regular node on the branch, to form 

 a new and weak axis through the nipple which forms such a distin- 

 guishing mark of the lemon as compared with the orange. The 

 nipple is possibly the result of the secondary rhythmic growth, 

 which in the Tangerine orange was able to advance to a perfect 

 fruit. From the limited opportunities of examining large quanti- 

 ties of lemons from seedling trees, I have not been able to demon- 



