231 



Spines. — Professor Lindley defines a spine as " the imperfect evo- 

 lution of a leaf-bud, and therefore a branch." That some branches 

 may be checked in their growth so as to be changed into spines, I 

 will not deny ; but the usual development of spines is not in accord- 

 ance with this view. They are found on the shoots of the current 

 year, and occupy ( as to time as well as position ) the place of a leaf- 

 bud ; in other words, they appear one year sooner than a branch, 

 under ordinary circumstances, can be developed at that point. 



Nettle Stings. — The extremity of the sting is at first hermetically 

 closed up by a small globular button, not unlike the button of a fen- 

 cing-foil, but placed obliquely, so that the slightest touch breaks it off, 

 when the sharp extremity of the tubular sting enters the skin, and 

 pours into the wound the venomousjuice lodged in the spongy elastic 

 receptacle at the base of the sting. If a nettle leaf be grasped with 

 violence, the hand is seldom injured ; owing to the fracture of the 

 sting itself, which cannot puncture the skin after its fine point has 

 been turned aside or broken off. 



Spiral Vessels on the Seeds of Collomia, 8^c. — Those who have not 

 examined them will be much gratified by placing thin slices of the 

 seeds, one at a time, under a microscope of moderate power, and ob- 

 serving the effect which immediately ensues when a drop of water is 

 added ; but they will be still more interested with the serpent-like 

 movements of similar vessels in the «c/(e«m of Salvia. If an unripe 

 berry of the mistletoe be examined under a microscope, a portion of the 

 internal viscous substance lying nearest to the seed will be found to ex- 

 hibit traces of similar spirals. May not the economy of all these be 

 the same ? 



Anthers of Viscum album. — I know of no analogous structure in 

 other plants : the anther is not valvular, and adheres, without any fi- 

 lament, to the surface of the petal. The pollen is contained in little 

 cysts imbedded in the substance of the anther, opening irregularly. 



William Wilson. 

 Orford Mount, Warrington, July 1, 1845. 



P. S. — If it be not a misemployment of the pages of the 'Phytolo- 

 gist' to correct an inadvertance in one of my former communications 

 (Phytol. i. 6 ), I beg to state that the leaves of the holly have the pe- 

 tiole articulated as in ordinary cases, but that the articulation in ao-e 

 is scarcely if at all perceptible. If the young leaves be examined 

 there can be no mistake. 



