SECTIONAL TRANSACTIONS.—K. 481 
nuclear division ; the wood structure—especially young stem and root wood; even 
the cuticular structures when all three species are kept in view; these and other 
aspects of structure all point to a close relationship with Sequoia. If the relationship 
holds between Athrotaxis and Taiwania which has been claimed by Sorger on certain 
points of vegetative structure, then the group of the Sequoideae of Saxton (Sequoiineae 
of Seward) may be a more extensive one than at present constituted. A. lawifolia 
may possibly be a wild hybrid between the other two species. 
traction in Oxalis and some Monocotyledons. 
The essential features of root contraction previously described for Oxalis incarnata 
are exhibited by other species of Oxalis including O. martiana, cernua, &c. 
Remarkably similar features, indicating a similar mechanism of contraction by 
longitudinal shrinkage, through degeneration of protoplasm, withdrawal of sap and 
collapse of cells in transverse zones, are also found in certain Monocotyledons, including 
Brodiaea lactaea, B. capitata, B. grandiflora and some Dactylorchids (e.g. Orchis 
incarnata). 
Further work on Oxalis incarnata has shown that a preliminary phase of true 
growth contraction precedes the more extensive contraction by longitudinal shrinkage. 
Prof. F. E. Luoyp.— 
(a) Conjugation in Mougeotia. 
Early phase. The preliminary contact of filaments prone to conjugate having 
been established, there is a local adhesion to the point of growth of the conjugation 
tube, where a stiff, water-insoluble mucilage acts as an adhesive. Follows a sharp 
bending away of both filaments on either side of the adherent area, sometimes 
accompanied by enlargement of the gametes. Both these phenomena take place 
without apparent change in the osmotic value of the sap. 
Fusion of the gametes begins after the resorption of the canal wall. At first there 
‘is a vigorous movement of cytoplasm in the tube, streams travelling in opposite 
directions between the gametic masses, of which the optically most readily appre- 
hended are the chloroplasts. The latter approach each other mutually within the 
tube, where they meet and where there is a coiling up and crowding in of the chloro- 
-plasts, nuclei and adherent cytoplasm. The utricular cytoplasm is left behind, this 
“never leaving the wall (de Bary). Threads of cytoplasm are drawn out by the moving 
chloroplasts. These threads offer resistance to the movement as well as others aid 
it, and the movement appears autonomous. It proceeds until an irregular mass is 
formed of the chloroplasts and adherent cytoplasm, too large for the definitive space 
~ available within the limits of the zygote to be. This ends the movement of approach. 
_ Follows the period of condensation during which water is thrown off and the zygotic 
~ mass takes on the definitive lens shape. There now begins an extraordinary activity 
of the cytoplasm external to the zygotic mass. This consists in the extrusion of 
large bubbles of cytoplasm in such profusion that it suggests the boiling of a very 
viscous fluid. Balloon-shaped bubbles extend out and wave to and fro, sometimes 
_ fusing and all collapsing at last. This abates only with the final condensation of the 
* zygotic mass. It would seem to be a method of rapidly throwing off water, but it is 
~ not clear that the mechanism is identical with that in Spirogyra, in which contractile 
4 vacuoles occur. 
: (b) Vampyrella lateritia—a Regurgitating Mechanism. 
__The behaviour of Vampyrella lateritia during and after feeding on Mougeotia has 
been recently studied and a remarkable activity in the rejection of presumably 
digestible material observed, by no means comparable to defecation. 
The individual in question began to feed on a pair of conjugants. The procedure 
of withdrawing the cytoplasm and chloroplasts is quite as described for Spirogyra 
(Lloyd, Protistenkunde 67, 219-236, 1929). The contents of both gametes were 
‘withdrawn together. After retiring from the emptied cells, the animal showed 
 disinclination to move away, yet seemed to be disquieted. Continued watching was 
rewarded by seeing pseudopodal activity setin. Thick, blunt, cylindrical pseudopodia 
were protruded five times in succession from various places. At the outer end of 
1931 4A 
| Prof. D. THopay and Miss A. J. Davey.—The Mechanism of Root Con- 
