ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 253 



may also be combined in a variety of ways. These terms (except the first) 

 apply to various modes of folding ; there are also a number of ways in 

 which the leaves may be rolled up before opening, viz. : — Spirally twisted 

 (eingerollt) (Musa) ; twisted right or left ; spiral and imbricate (iibergerollt) 

 (Escallonia macrophylla) ; spiral and valvate (gerollt) (Specularia per- 

 foliate) ; channelled (Linum usitatissimum) ; cornet- shaped (Spironema 

 fragrans) ; involute (Nymphsea) ; revolute ; circinate ( Utricularia montana). 



With regard to the value of vernation for systematic purposes, there 

 are very few families in which the mode is uniform throughout all the 

 species. In Nymphaeaceaa the floating leaves are always involute on both 

 sides ; in Polygonacefe the leaves are always revolute on both sides ; in 

 Scitamineas spirally involute ; in Mimoseas the pimias are always fiat. In 

 other families the vernation is uniform throughout, with the exception of 

 a few genera or species. Within the genus the mode is usually the same 

 with the same form of leaf, but most generally varies when the form of 

 leaf varies. 



The vernation of leaves is also influenced by the nature of the vena- 

 tion, by the consistency of the leaf, and by the presence of stipules or leaf- 

 sheaths. The floating or submerged leaves of water-plants appear to be 

 flat or rolled in vernation, never folded. The purpose of the different 

 modes is the protection of the leaves in the bud-condition. The position 

 of the leaves assumed during sleep or under the influence of irritants is 

 usually partially, but not entirely, a reversion to the position in vernation. 



Double Leaves.* — By a double leaf Dr. M. Kronfeld understands one 

 which bears two laminse on one petiole. He distinguishes between an 

 epidiphyllum, where the growth of the lamina has been interrupted at a 

 particular spot, and a paradiphyllum, resulting from dichotomy of the 

 lamina. The former occurs normally in Dionsea, and probably also in 

 Nepenthes ; the latter chiefly in particular varieties, especially of ferns, 

 such as Asplenium Trichomanes ramosum. 



Pitcher-like leaflets of Staphylea pinnata.j — M. Lachmann describes 

 the not uncommon formation of pitchers by some of the leaflets in this 

 plant. It results from the more or less complete union of the edges of 

 the lamina, so that either the whole, or only the upper part of the leaflet 

 takes the form of a cornucopia ; in the latter case the normal lower 

 portion of the leaflet is connected with the pitcher by means of a stalk. 

 He concludes from analogy that in Nepenthes the pitcher must be 

 regarded as the terminal portion of a lamina, the basal part of which 

 remains flat. 



Clinging-Plants4 — Dr. E. Huth describes the various means by 

 which plants attach themselves to the fur or skin of animals, by hooked 

 or barbed hairs attached to the seed-vessels or some other part of the 

 plant, or by other contrivances, for the purpose of propagation. Under 

 each natural order the plants are named and described in which these 

 contrivances are found. 



Heterophylly.§ — According to Dr. F. Krasser, when two different 

 forms of leaf occur on the same plant, it may be an example of true 



* SB. K. K. Zool.-Bot. Gesell. Wien, xxxvii. (1887) pp. 74-6. 

 t Bull. Soc. Bot. Lyon, 1886. See Bull. Soc. Bot. France, xxxiv. (1SS7), Rev. 

 Bibl., p. 151. 



J Uhlworm u. Hiinlein's Biblioth. Bot., Heft ix., 1S87, 36 pp. and 78 figs. 

 § SB. K. K. Zool.-Bot. Gesell. Wien, xxxvii. (1887) pp. 76-8. 

 1888. T 



