TRANSACTIONS 



OF THE 



SOUTH AFRICAN PHILOSOPHICAL SOCIETY. 



Vol. XVIII. 



ON THE DEVELOPMENT OF THE OVULE AND 

 EMBEYO-SAC IN CASSIA TOMENTOSA, Lamk. 



(Bead March 27, 1907 ) 



(Plates I.-II.) 



By W. T. Saxton, B.A. 



The development of the ovule and embryo-sac in plants has 

 been investigated very fully, especially during recent years, and the 

 normal course of events has been thoroughly worked out in several 

 cases. There are, however, in this species of Cassia, certain pecu- 

 liarities of interest, which are described below. It has been found 

 most conducive to a clear account to give all the stages of develop- 

 ment, as far as they have been investigated, normal as well as 

 abnormal. 



The species is a South American one, not native in Cape Colony, 

 and the material has been obtained from private gardens in Cape 

 Town. 



It is proposed to give a short account of the development from 

 about the archesporial stage to the formation of the definitive 

 nucleus in the eight-celled embryo-sac. 



The young ovule at about the archesporial stage is distinctly 

 campylotropous (Fig. I.). No definite archesporial cell or cells are 

 clearly recognisable, but one towards the centre, somewhat larger 

 thai! the surrounding cells (M.M.C., Fig. I.), is probably the 

 megaspore mother-cell just becoming differentiated. The primordia 

 of the outer (O.I.) and inner (U.) integuments are shown distinctly 



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