506 PROFESSOR DICKSON ON SOME ABNORMAL CONES OE PINUS PINASTER. 



calmly to pursue the investigation, rejecting all premature hypotheses, which 

 can never be more than substitutes for science."* 



In their essay on the arrangement of curviserial leaves, the brothers Bravais 

 approach this question somewhat more closely. In dismissing the idea of 

 abortion in such cases, Braun occupied his position mainly, it would appear, in 

 consequence of the absence of any supporting evidence. The celebrated 

 French authors, on the other hand, actually observed, in capitula of Dipsacus 

 and in fir cones, certain cases where, in the same inflorescence, there occurred 

 an actual change from one spiral system to another, accompanied by a diminu- 

 tion in the number of secondary spirals. They do not appear, however, to have 

 had a very definite idea as to the exact manner in which this diminution in 

 the number of secondary spirals is effected. Although on the whole they 

 seem inclined to treat the phenomenon in question as the result of abortion of 

 secondary spirals, — as, for example, when referring to certain capitula of 

 Dipsacus with 16 and 26 as the numbers of the secondary spirals at the base, 

 suddenly changing to 15 and 26, or 15 and 25, or 16 and 24, they state that 

 here " there is no doubt as to the abortion of the missing spirals, since they 

 are as evident as their fellows at the base of the capitulum,"t — yet, in the 

 resume at the end of their essay, considerable uncertainty is indicated in the 

 sentence, that " the convergence of two spirals into one is to be explained by 

 partial abortion of one of the spirals, or, if preferred, by the coalescence of two 

 spirals into one. "J 



Of cases of this kind occurring in fir cones, MM. Bravais describe two 



cones of Pinus Pinaster {Pin maritime), one where the lower part of the cone 



12 3 5 8 



exhibited secondary spirals 7 S, 12 D (series -, -, =, — , — , &c.),while towards 



_ •> / i _ it' 



1 1 2 3 5 



the apex the arrangement changed to 7 S, 11 D (series o>j.'W>tt>Tq' & c -)>§ 



and a second, in which the lower four-fifths of the cone exhibited secondary 



12 3 5 



spirals 9 S, 13 D (series -, -, — , — , &c), while at the upper fifth the arrange- 



ment changed, by suppression of one of the spirals by 9, to 8 S, 13 D (ordinary 



112 3 



series -, -, -, -> &c.)||. Such cases, along with some others, chiefly in capitula 



_■ o D o 



of Dipsacus sylnestris, lead MM. Bravais into a discussion of the general 

 question of the transition from one arrangement to another, involving a change 

 in the number of secondary spirals. As regards their "curviserial" forms, 



* Braun, Vergleichende Untersuchungen iiber die Ordnung der Schuppen an den Tannenzapfen : 

 Nova Acta Acad. C.L. xv. 1, p. 316. 



t L. et A. Bravais, Sur la disposition des feuilles curviseriees. Ann. des Sc. Nat. 2 me s&r. vii. 

 p. 100. 



% L. c. pp. 106, 107. § L. c. p. 93. || L. c. p. 103. 



