241 



The rhythmic waves of growth are not all of equal measure. As in 

 jumping a ditch, a boy may now rest exactly where he lands, and now 

 have to continue several paces before final rt st, so does the wave force 

 in growth vary in intensity. In the process of the metamorphosis of a 

 branch with its various modes into a flower and finally a fruit, the 

 expenditure of force in the ar Testation of axial growth and the develop- 

 ment of the appendages to petals, stamens and carpels is exactly meted to 

 the results, — now it is short of the mark, and the axis starts under 

 another rhythmic movement the next time to be arrested for good 

 and all. 



It is this succession of growth rhythms that produces the double fruit 

 oranges, but the phenomenon is not confined to the citrus tribe. In 

 the formation of cones in the coniferous family the branch in its axial 

 growth is usually wholly suppressed ; but occasionally, 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 ihe apex of the cone results. In Rosacea) the 

 same phenomena are by no means uncommon. One rose blossom* will 

 push out from the centre of another, and a small branch bearing aminature 

 pear has been known to spring from the crown of a pear of normal 

 character beneath it 



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

 the variety of orange known as the Tangierine, and this by reason 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 morpho- 

 logical conception. It is not rare to have specimens of Tangierines in 

 which are from five to ten abortive carpels at the base of the fruit. In 

 these cases the well defined axis, usually in the common 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 Tangierine 

 has always a flattish or oblate form. The utter suppression of the axis 

 at the point of its formation naturally favouring 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 natm*ally 

 leads to a more elongated form. Ihis hypothesis is supported by 

 examining a half section of the lemon taken longitudinally. 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 distinguishing mark of the 

 lemon as compared with the orange. The nipple is possibly the result 

 of the secondary rhythmic growth, which in the Tangierine orange was 

 able to advance to a perfect fruit. From the limited opportunities of 

 examining large quantities of lemons from seedling trees, I have not 



* Mr. iS. Moxsy lately sent an interesting example. [Ed. 13n J 



