1 86 MORPHOLOGY AND LIFE HISTORY 



(d) Opposite the connective may often be seen a 

 cross-section of the filament, with its vascular 

 bundle. 



(e) The numerous, conspicuous blue-stained bodies 

 are starch grains. 



(/) Note the epidermis, one cell thick. Does it 

 cover the entire surface? Does it contain 

 starch grains? Find numerous stomata, each 

 with a small, underlying air-space. 



(g) At each side of the section will be seen two 

 sporangia, containing the large microspore- 

 mother-cells (pollen-mother-cells) , with promi- 

 nent nucleus. Observe the network of chrom- 

 atin within each of these nuclei. The mother- 

 cells adhere more or less closely, depending 

 upon age. Their final separation from other 

 cells, and from each other, marks the first 

 separation of the gametophytic from the 

 sporophytic generation. The mature micro- 

 spore-mother-cell is the first stage in the develop- 

 ment of the male gametophyte (cf. 6 (a), 

 below, p. 1 88). 



(h) Around the mother-cells note a layer of elong- 

 ate cells, radially arranged, and with nuclei 

 more or less disorganized. These are the 

 tapetal-cells. Together they form the tapetum. 



(i) Between the tapetum and epidermis lie the 

 middle layers of cells forming the wall of the 

 sporangium. How many cells thick is it? 



(k) Make a drawing 8 cm. in longest measure, 

 showing all features observed under 4, (a)-(k) . 



(I) By two successive divisions each pollen-mother- 

 cell forms four microspores (young pollen- 

 grains). They thus arise in tetrads. 



