Nov. 23, 1888.] 



SCIENTIFIC NEWS. 



5 2 9 



ON VERNATION AND THE METHODS 

 OF DEVELOPMENT OF FOLIAGE, 

 AS PROTECTIVE AGAINST RADIA- 

 TION. 



A Paper read by the Rev. George Henslow, M.A., 



F.L.S., F.G.S., before the Linnjean Society. 



{Concluded from p. 506.) 



THE tile-like arrangement of the uppermost stipules 

 and subsequently ol the leaves themselves, thus pro- 

 tecting the edges of the vertically placed leaves beneath 

 them, reminds one of a very similar method of pro- 

 tection in Trifolium repens when asleep. In this plant 

 the two basal leaflets rotate so as to bring their upper 

 surfaces in contact and their blaces vertical, while the 

 terminal leaflet revolves through half a circle and comes 

 down upon the upper edges like an arched roof above 

 them* (figs. 5 and 6). 



Fig- 5- 



Fig. 6. 



Trifolium repens. 



Fig. 5. — Leaf during Day-time. Fig. 6. — Asleep during 

 Night-time (after Darwin). 



In the case of the Hazel the process is much the same, 

 but with Ampelopsis Veikhii the blade spreads out at 

 once, however young, and is not conduplicate; but 

 as it hangs vertically from its very birth to its fall, 

 it does not require any further protection beyond what 

 the leaves above it happen to supply by overhanging 

 it. The branches of this species cling so tightly to the 

 wall that very possibly a good deal of heat is radiated 



Fig. 7- 



Fig. 7. Rose. Younger leaf erect ; older with petiole curved 



and half-developed leaflets. 

 Fig.' 8. Pea. Leaf emerging from between the stipules ; the 



leaflets conduplicate. 

 Fig. 9. One stipule removed to show the erect bud within 



and protected by the stipules. 



from the wall itself on to the back, i.e., the underside of 

 the leaf. The Beech differs from the Lime in having its 

 young leaves dependent only, and not protected. They 

 are feebly conduplicate, but with a plicate surface, and 

 the stipules do not form any protection ; and, contrary to 



* Darwin, "Movem, of plants," p. 349> fig- 141. 



what takes place in the Lime, the older, basal leaves, in- 

 stead of covering the younger ones, hang below them 

 the slender shoot curving at the apex so that the ter- 

 minal and younger leaves have a tendency to be vertical, 

 but not to so pronounced an extent as in the Lime. It 

 may be noticed that the Beech does not open its buds 

 till a later period than the Lime, and at a time when 

 spring frosts are nearly over. The Spanish Chestnut 

 agrees closely with the Beech, the leaves being at first 

 subconduplicate, and similarly plicate, while each leaf 

 on expansion is spread out below the terminal shoot. 

 Both trees belong to the same section of the Cupulifera:. 

 II. Compound Leaves (i) Opposite : (i) erect. — The 

 Ash and the Elder are illustrations. As with simple 

 leaves, the leaflets of compound leaves are almost in- 

 variably conduplicate ; the Elder, however, as stated 

 above, having the margins of the leaflets involute as well. 

 They all stand erect at first and only gradually assume 



Fig. 10. 



Clover. 



Fig. 12. Wood—sorrel : a, nat. size ; b, magnified ; c, vertical 

 aspect, in diagram as seen asleep. 



the horizontal position on their complete development. 

 The leaflets of the Ash are at first similarly clustered 

 together, but simply conduplicate. With Weeping Ashes, 

 in order to place the young leaves erect, the petiole is 

 obliged to make a very strong curve upwards, not 

 necessitated in the ordinary form of the tree. 



(ii) pendulous. I have not met with an instance of 



Fig 



Fig. 14. 



Fig. 15. 



Horse 



Chestnut. 



Lupmus pilosus. 

 Leaf, seen laterally, 

 asleep at night-time. 



(After Darwin.) 



Walnut. 



opposite compound leaves being pendulous in the young 

 state. 



(2) Alternate ; (i.) erect. — Of compound leaves there 

 are the two types, digitate and pinnate. Of the former, 

 Lupin will illustrate this position. A specimen with 

 white flowers had the leaflets all conduplicate at first 

 and erect, forming a small but dense mass. Of the 

 pinnate type with erect leaflets many instances might 

 be mentioned, as, e.g., Goutweed, Chervil, Sumac, Rasp- 

 berry, and Rose. As a rule, besides being conduplicate 

 and, in some cases, plicate in addition, the leaflets are 

 all pressed together laterally, thereby affording a certain 

 amount of mutual protection. This is well seen in the Rose 



In the case of the Rose the developing bud is protected 

 by the adnata stipules (fig. 7), and the young leaf, wher^ 



