TRANSACTIONS OF SECTION K. 10GB 



They separate from one another a^ain, and the smaller nucleus then increases in 

 size until it attains the same proportions as the larger nucleus. 



6. At a very late stage in the development of the zygospore two nuclei can still 

 be observed, but there are indications that these two nuclei fuse together at a still 

 later stage. 



The^following Papers were also read : — 



2. On the Peltation of Leaves. By Professor C. DE Candolle. 



The object of the present paper is a comparative study of peltate leaves, with 

 special reference to the number of species possessing such organs, their distribution 

 amongst the various natural orders, and their respective mode of growth. 



Pitcher-shaped leaves — that is to say, natural ascidia — are here considered as 

 being homologous with ordinary peltate leaves, a view long ago sustained by 

 Baillon and based on the organogeny of both sorts of leaves. Accordingly, by the 

 general expression ol i->eltation of leaves, the author includes peltate leaves proper 

 and ascidia. 



As the result of bibliographical researches the author has succeeded in 

 cataloguing 308 phanerogams having peltate leaves proper and 49 having ascidia- 

 shaped or ascidia-bearing leaves. A general survey of all these cases of peltation 

 has led him to the following results : — 



1. The peltation of leaves is very rare, the species in which it has as yet been 

 observed being an insignificant minority in the total number of actually known 

 phanerogams, estimated at about 110,000 species. 



2. The peltation of the leaflets of compound leaves is still more exceptional, 

 only two such cases hanng so far been recorded — namely, in the genus Thalicti-um. 



3. Peltate leaves proper and ascidia-shaped leaves are unknown amongst 

 verticillate and extremely rare amongst opposite leaves. 



4. Sarraceniacete and Nepenthacese being placed on one side, the peltation of 

 leaves is always an exceptional character in each order or genus in which it occurs. 

 Cases of peltation appear, so to say, at random in various natural orders, between 

 which they are very unequally distributed. Consequently there is no correlation 

 between the peltation of leaves and the floral characters of plants. 



5. While there is an evident functional adaptation of ascidia-shaped leaves to 

 the biology of the plants which produce them, peltate leaves proper on the contrary 

 do not seem to possess any such adaptation, so that they must, for the present, be 

 looked upon merely as an indication of an excess of development not as yet 

 accounted for. 



6. The great scarcity of peltate or ascidia-shaped leaves amongst actual 

 phanerogams is difficult to reconcile with the fact that teratological ascidia are of 

 rather frequent occurrence. 



7. The peltation of leaves is in no correlation with the geographical distribution 

 of plants. However, phanerogamic species in general being immensely more 

 numerous in the inter-tropical than in the extra-tropical regions, peltate-leaved 

 plants are necessarily also much more numerous in the former than in the latter 

 zones. 



.3. Changes in the Sex of Willoios. 

 By I. H. BuRKiLL, M.A., Royal Gardens, Kew. 



In the genus Salix flowers of both sexes are occasionally present in the same 

 catkin, and one sometimes finds that the sexual organs are intermediate in struc- 

 ture between stamens and carpels. By using the published records and by 

 availing myself of the large accumulation of material for study in the Herbaria 

 at Kew, Cambridge, in the British Museum, and at the Jardin des Plantes, Paris, 

 I have gathered together a number of facts which may be of interest. 



Firstly, it is obvious that these abnormalities, though widely distributed in the 

 species of Salix, are much more common in some sections than in others. The 



