486 • ■ PROCEEDINGS OF SECTION D. 



impermeable by water or vapor. The stomates are doubly protected — 

 first by their position in the cavities, and second by the plug of hairs 

 which fills the cavity and closes its mouth. 



But the same adaptations are equally useful to the plant in wet 

 weather. The projecting tufts of hairs on the under side prevent water 

 spreading over the under surface and making its way into the crypts, 

 and so the stomates are not choked with water and prevented from 

 fulfilling their function of exhaling the superabundant moisture which 

 the plant takes up in wet weather, and which it is necessary should be 

 got rid of as speedily as possible. An illustration of this action of the 

 hairs may easily be seen if a leaf is dipped in water. The upper surface 

 is wetted and shows a thin film of water all over it. But the under 

 surface remains dry, the water gathering into drops and falling off as 

 if the leaf were greasy. 



EXPLANATION OF PLATES. 

 Plate I. — Figs. 1 and 2. Hairs from surface of young leaf. 

 Fig. 3. Hair from midrib of young leaf. 

 Fig. 4. Diagrammatic section of leaf. 

 Fi?. 5. Outline of stomate. 

 Fig. 6. Hairs from interior of crypt. 

 Plate II. — Photograph of under surface of leaf, showing tufts of 

 hairs projecting from crypts X 10. 



Plate III. — Nature print of leaf showing venation. 

 Plate IV. — Section of leaf, X 100 ; s, stomates seen in section ; 

 hf hairs of crypts. 



4.— A PRELIMINARY NOTE ON HETEROPHYLLY 

 IN PARSON SI A. 



By L. COCKAYNE, Ph.D., Cor., F.B.S., Ed. 

 [With Plate.] 



Parsonsia is a small genus of lianes containing some 33 species, 

 found in tropical Asia, the Malay Archipelago, New Guinea, New 

 Caledonia, Australia, and New Zealand; in fact the distribution is 

 exactly in accord with the generally accepted theory of a former land 

 extension of New Zealand northwards. The headquarters of dis- 

 tribution is New Caledonia, which contains 23 species. Australia is 

 also fairly rich with four or five, while New Zealand has two, or perhaps 

 three. 



If a number of seedlings of the most common New Zealand species, 

 Parsonsia heteropJiylla, be examined for the first time the number of 

 leaf-forms are quite bewildering, and it looks apparently impossible 

 to find any regular sequence of development. But a closer examination 

 shows this not to be the case, and. that there is a definite process of 

 development and change. This complexity arises from the fact that 

 there are two distinct types of leaf — a primary short broad leaf and a 



