Feb. 1891.] BOTANICAL SOCIETY OF EDINBURGH. 67 



Development of the Maceosporangium in Myosurus 

 minimus, Linn. Part I. By Gustav Mann. 



The author pointed out that in Myosurus minimus and in 

 Ranunculus sceleratus the cells of the periblem-layer elongate 

 greatly in the developing nucellus, formiug a mass of arche- 

 sporial tissue ; the central cell of this tissue, i.e., the one 

 opposite the plerome-element, outstrips the others in growth, 

 its nucleus becomes of large size, the nucleolus remaining 

 small, and by division it gives rise to three or four cells, 

 which may be placed differently according to external condi- 

 tions, such as pressure on the developing nucellus, &c., but 

 which are mostly arranged in a vertical row. This row, the 

 result of division of the physiological archesporial cell, is 

 surrounded by cells derived from the non-physiological 

 archesporial cells. All the walls of this row show gelatinous 

 swelling, the walls of the cell giving rise to the embryo- 

 sac included, except the wall abutting on the plerome- 

 element. The reason for the greater development of the 

 physiological archesporial cell, as also of that special cell 

 which gives rise to the embryo-sac, is the greater supply 

 of nourishment brought to these two cells by the plerome- 

 elements, with which they lie in immediate contact ; in 

 support of this view may be urged the fact that in the 

 developing sporangia of Selaginella and Tmesipteris the 

 spore-tissue next the stalk develops quicker than that at 

 the apex of the sporangium. 



On Temperature and Vegetation at the Botanic 

 Garden, Glasgow, during January 1891. By Egbert 

 BuLLEN, Curator. 



Prost was registered on twenty nights during the month, 

 and on several other nights the mercury was little above 

 the freezing point; generally the readings were light, the 

 total for the twenty nights being only 119°. The lowest 

 reading was 13° during the night of the l7th. On five 



