92 Morphology BOOK i 



leaf is reduced to a sessile limb completely converted into 

 either one or two ovules. 



Yet another theory was due to Penzig in 1894, which was 

 that the seminiferous scale is formed by the two lateral 

 lobes of the carpellary scale turning inwards till they 

 meet, fusion of the margins then taking place. 



Like all the floral members, the stamen in 1860 was held 

 to be a metamorphosed leaf, and its various parts were 

 accordingly attributed to particular foliar regions. Cassini 

 and Roeper put forward the view that the two anther lobes 

 are the swollen lateral halves of the blade. The pollen sacs 

 must consequently be excavations in the tissue of the 

 leaf ; the furrow between the two anther lobes must 

 represent the leaf margin, and the two pollen sacs of each 

 lobe must be on different faces of the blade. Sachs com- 

 bated this view, bringing forward the researches of von 

 Mohl on certain abnormal developments. He suggested 

 as preferable the theory that the whole structure is of a 

 sporangial nature. Reviewing, too, the facts of histological 

 development, he said, ' The origin of the pollen mother- 

 cells and the 'development of the wall of the separate 

 pollen sacs call to mind so vividly in all essential features 

 the corresponding phenomena in the sporangium of Lyco- 

 podiaceae and even of Equisetaceae, that it may be assumed, 

 until more exact observations bring something different to 

 light, that each pollen sac (i. e. each loculus with its wall) 

 corresponds to a sporangium, and hence also to a single 

 pollen sac of Cycadeae and Cupressineae.' 



Here we have the first presentation of the views now 

 current, which only waited for the work of Goebel to give 

 a satisfactory exposition of the morphology of the stamen. 



The theory of the stamen as essentially a modified leaf 

 was contested on other grounds, particularly on certain 

 anatomical researches carried out by many investigators. 

 The first of these and the most important were made by 



