in the Lycopodiacese, Equisetacese, &c. 435 



the leaves from that of the flowers, we have supposed the sup- 

 pression of alternate whorls, and of the alternate leaves of each 

 whorl preserved, making a suppression of 75 per cent, of the 

 leaves. In other cases, the suppression of leaves is only 

 50 per cent., as in the case of most Endogens whose flowers 

 consist of alternating whorls of three organs. If we suppose, in 

 this case, the suppression of alternate whorls, and a spiral 

 arrangement, the divergence will become 3. 



In the case of opposite-leaved plants, the suppression of alter- 

 nate whorls will give us the distichous arrangement, ^, at an 

 expenditure of 50 per cent, of leaves. 



In these and many other cases, we can deduce, by the hypo- 

 thesis of suppression, the alternate-leaved phyllotaxis from the 

 whorled ; and it is worthy of remark, and leads me to my more 

 immediate subject, that the whorled arrangement, which is 

 rare (with the exception of opposite-leaved plants) among Exo- 

 gens and Endogens, was the common arrangement of leaves 

 among the Coal-plants, and, so far as we know, among the 

 plants of the Old Red Sandstone, which forms the base of the 

 Carboniferous rocks. 



The Palseozoic trees and plants are referred to natural orders, 

 resembling in many respects our recent Lycopodiacese, Equise- 

 tacea3, and Ferns. In all these orders, the whorled phyllotaxis 

 of the kind I have described commonly prevails. 



I. Lycopodiacese*. 



1. Lycopodium dendroideum (Herb. Oakes). Canada. Leaves 

 of stem arranged in alternate whorls of 7 leaves in each. Diver- 

 gence of whorl = y 1 ^. 



2. L. densum. New Zealand. Leaves of stem in alternate 

 whorls of 7 each. Divergence = y 1 ^. 



3. L. clavatum. Massachusetts. Leaves of stem and flower- 

 stalk in alternate whorls of 7 each. Divergence = y 1 ^. 



4. L. divaricatum. Nepaul. Leaves of stem in alternate 

 whorls of 11 each. Divergence = ^. Leaves of flower-stalks 

 in alternate whorls of 8 each. Divergence = y 1 ^. 



5. L. (n. sp.). Caraccas, S. America. Leaves of lower stem 

 in alternate whorls of 7 each. Divergence =-. T ^. Leaves of 

 upper stem in alternate whorls of 2 eact (i.e. opposite-leaved). 

 Divergence = J. 



6. L. volubile. New Zealand. Leaves ui lower stem in alter- 

 nate whorls of 4 each. Divergence = . Leaves of upper stem 

 in alternate whorls of 2 each. Divergence = . 



* The plants examined by me for the purposes of this paper are those 

 preserved in the Herbarium of Trinity College. 



29* 



