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248 



DK. M. T. MASTERS ON THE MORPHOLOGY, 





The leaves on the erect shoots being crowded and overlapping 

 one another more completely than elsewhere, are less favourably 

 situate as regards access of light than those on the side shoots, 

 in which, owing to the arrangements before mentioned, the in- 

 ternecine competition is less severe, hence one reason for the 

 speedier fall of the leaves from the erect shoots aud the more 

 crowded parts of the tree, and the comparatively naked inter- 

 spaces between the whorls of branches. 



The disposition of the leaves of these plants indeed seems to 

 be arranged to secure an equitable share of light and as equal 

 exposure as possible to the whole mass of foliage, thus reducing 

 competition among individual leaves to the greatest possible ex- 

 tent. In some cases, the arraugement is such as to secure the 

 exposure of the stomatif erous surface to the light and heat, as in 

 cases where the leaves are appressed against the stem in such a 

 way as to leave the stomate-bearing surface free 



The movements in the leaves of many Conifers during the season 

 of active vegetation particularly, and which take place uuder the 

 influence of sunlight, have presumably a similar object. In Picea 

 ajanensis the stoinata are on the upper surface of the leaf, and 

























srreen 













dorsal surface is exposed to the light. The uplifting of the 

 leaves, however, permits the stomatic surface to be exposed upon 

 occasion f. Mr. Moggridge alludes to this subject in a note on 

 the movements of the leaA r es of Pinus halepensis (' Journal of 

 Botany,' Feb. 1, 1867). The leaves of this tree in warm sunny 

 weather are fully separated, but if the sky become overcast they 

 close partially ; the sirocco produces a similar but more marked 

 effect, but in rain the leaves collapse, giving the tree a most me- 

 lancholy aspect. A similar change is observable in most Pines 

 in summer and winter respectively, at which latter season they 

 are nearly parallel, not divergent. Probably the state of things 

 in some cotyledons, as before mentioned, and in the primordial 









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* E. Mer, " Da Tinfluencc tie l'oiubre et de la luiniere sur la structure, Torieu- 

 tation et la vegetation des aiguilles (X Abies e.vcelsa" in Bull. Soc. Bot. France, 

 t. xxii. p. 199, t. xxiv. p. 109, t. xxvi. p. 15, t. xxvii. p. 23. and t. xxx. (1883) 

 p. 40 ; and Comptes Rendu*, April 16, 1883. 



t Ohatin, " Sur les niouvements penodiques des feuilles $ Abies Xordiuan- 

 niana? in Bull. Soc. Bot. France, xxiii. p. 103 (1876). Masters, "On the Ee- 

 lation between Morphology and Physiology in the Leaves of certain Conifers," 



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