700 REPORT— 1886. 



the cases of Ficus and Pandanus, and also of Hhizopliora, though it is to be noted 

 that in CWdyline shoots are the members employed, while roots are used in the 

 other cases named. 



3. Note on Apospores m Polvsticlium annulare, var. pulcherrimum. 

 By Professor F. O. Bower. 



Specimens were shown iUustratiu"; the above peculiarity, which has been 

 recently observed in a plant from a locality quite distinct from that where the 

 original plant was taken some twenty j-ears ago. 



4. On the Formation and Escape of the Zoospores in Saprolcgnice. 

 By Professor Hartog. 



5. On the Germination of the Spores o/ Phytophthora iufestans. 

 By Professor Marshall Ward, M.A. 



G. Two Fungous Diseases of Plants. By W. B. Grove, B.A. 



The first was the ' Eucharis disease,' which has been shown by the author to 

 be due to the fundus, Sacc/uiromi/ces f/lutinis. It attacks other bulbs besides 

 Eucharis, and may be known by producing reddish spots. It can be killed by 

 growing the bulbs in a considerable heat, or by sulphide of potassium. 



The second was a 'Viola disease,' attacking cultivattd species of Viola. It is 

 due to an QEcidium and its accompanying Puccinia, known respectively aa 

 (Ecidium depauperans and Puccinia ayru. It has only been observed in two or 

 three districts, as yet; and does considerably more harm to its hosts than the 

 similar disease which is common on Yiota canina. 



7. Preliminary Notes on the Autumnal Fall of Leaves. 

 By Professor W. Hillhouse, M.A., F.L.S. 



So far as these experimental investigations — commenced in the autumn of 1882 

 and stiU in progress — are concerned, the question of the autumnal fall of leaves has 

 been approached from two standpoints. 



(1) The mechanism of leaf-fall. 



(2) The transfer of the cell-contents from the leaf. 



(1) The Mechanism of Laf-fidl. — It appears to be certain that the dissociation 

 of leaf and branch takes place by the formation, by means of renewed cell-division 

 in the basal plane of the leaf-stalk, of a layer of cells, which the author proposes to 

 call the ahscies-layer. The absciss-layer is produced by new dividing walls being 

 formed across the cellular tissue of the base of the leaf-stalk. It is clearly recog- 

 nisable, not merely by means of these walls, but also by its marked quantity of pro- 

 toplasm, and the presence usually of numerous small grains of starch. The exact 

 position of the absciss-layer slightly varies, always outside the periderm line of the 

 branch, and usually sloping inwards and upwards. It is formed usually very shortly 

 before the fall of the leaf. In some cases no absciss-layer is formed, and the leaf 

 does not fall normally. The formation of the absciss-layer may be either preceded, 

 sometimes by a fair interval of time, or succeeded by "the formation, on the stem 

 side of it, of a periderm ; this likewise by new dividing cells being formed in a pre- 

 existing cellular tissue. This periderm lies usually more or less in the line of that 

 of the branch, and becomes continuous with it. The cells outside the periderm 

 shrivel. 



The author's experiments tend to show that the fall of the leaf arises from 

 the increased turgescence of the cells of the abscis.s-layer, owing to their osmotic 

 activity. These become strongly rounded ; their adhesion equally diminishes. 



