632 



REV. Q. HENSLOW ON VERNATION AND FOLIAGE 



pressed closely together laterally and suspended vertically. The 

 petiole is suberect in the Laburnum and Clover, but strongly 

 Fig. 10. Fig. 11. Fig. 12. 



Fig. 10. Laburnum. Fig. 11. Clover. 



Fig. 12. Woodsorrel: a, nat. size; b, magnified; c, vertical aspect, in diagram 



as seen asleep. 



curved at the apex in the Wood-Sorrel, so that the minute leaf 

 is under the concave end (fig. 12, a and b). When the leaf of 

 the Oxalis is asleep, the leaflets fall vertically and bring their 

 undersides in contact (fig. 2, c), but never resume the conduplicate 

 condition again. The sleeping condition of Clover has been 

 described above ; but here, as in all other instances, conduplication 

 once lost is never resumed *. 



This seems to indicate that the danger from exposure in the 

 very young state being much greater than in the adult, the pro- 

 tection is correspondingly more perfect. 



In the Horse Chestnut (fig. 13) the digitate leaf has at first all 



the leaflets dependent and more or less covering one another. 



This is exactly similar to the condition of the leaflets of Lupinus 



pilosus when asleep, as described by Mr. Darwin t (fig. 14). It 



Fig. 14. 

 Fig. 13. 



Fig. 15. 



Lupinus pilosus. 

 Leaf, seen la- 

 terally, asleep at 



Horse Chestnut. f£ ht " ^ . Walnut. 



Alter Darwin. 



* This is due to the fact, at least in Clover, that a thick layer of chlorophyl- 

 laceous tissue is developed over the fibro-vascular bundle of the midrib, thereby 

 preventing the two halves closing again. 



t L. c. p. 341, fig. 137. 



