Vol. 26 



No. 3 



BULLETIN 



\ 



OF THE 



TORREY BOTANICAL CLUB 



MARCH 1899 



■ 



On the Development of the Pollen Grain and the Embryo-sac in 



Bignonia venusta 



By B. M. Duggar 



(Tlates 352-354) 



SpORAXGIAL and ARCIIESPORL'VL DEVELOrMENT 



TJie viicrosporic Archesporitim and Sporangiitni 



Before the flower bud opens, median transverse and longi- 

 tudinal sections of an anther of Bignonia venusta show the pollen 

 mother-cells occupying four boat-shaped layers, as seen in cross 

 section in Fig. 3. Each layer is a single cell in depth, and the 

 general form of the archesporial areas somewhat closely resembles 

 that characteristic of Solanaceae, Labiatae, etc., as described by 

 Warming,* and as figured by him for Datura Stramoiiuni and 

 MefitJta aquatica, 



m 



In Bignonia I have studied the archesporium and its invest- 

 ments in some detail, beginning with the archesporial and wall 

 layer fundament. In Fig. i, a cross -section of an anther from a 

 bud of I to 2 mm. in diameter, it will be seen that the outer layer 

 of periblem in two considerable regions on each side of a radial 

 line is somewhat richer in protoplasmic contents, and it would 

 seem to be already slightly differentiated as a fundament. General 

 placental growth is now largely confined to the regions ;r, x. 

 Placental growth, however, soon becomes more marked at f, y, 

 and so continues until the general form is that of Fig. 2, Even 



* Warming, E. Untersuchuiigen liber rollcnbildende PhyHome unci Kaulome. 

 Bot, Abhaudl. Hanstcin, 2: I-90. 1873. 



[Issued 18 March, 1899 ] ( 89 ) 



