CHAPTER XIV. 



THE STAMEN AND POLLEN-SAC. 



All the farts brought forward in the preceding chapter may he 

 observed under a hand lens, or under low powers of the microscope. 

 But observation under higher powers is necessary for obtaining an 

 intelligible grasp of the details of propagation in Seed-Plants. The 

 minute structure of -the outer envelopes can be dismissed briefly. 

 The sepals, which are usually green and relatively firm in texture, 

 repeat in their structure, though on a reduced scale, the features of 

 foliage leaves. Their epidermis bears stomata, and the mesophyll 

 below, though small in quantity, contains chlorophyll, and is traversed 



riG. lyo. 



Singh' r-fU tif ,i petal of Sejuria, showing numerous chromoplasts of semi-erystalHne 



form- ( ■ 800.) (.\fter Sehimper.) 



by vascular strands after the manner of other leaves. The petals also, 

 though wider in expanse and more delicate in structure, are constructed 

 on a similar plan. But the green of chlorophyll is replaced in them 

 by other colours. The blues and pinks are chieflv due to colouring 

 matters dissolved in the ii'atery cell-sap of the cells. But the red and 

 yellow colours are given by bodies called Chromoplasts. These are 

 often of irregular crystalline form. They are derived from the 

 plastids of the young cell, and multiply like them by fission (Fig. 190). 

 Sometimes both sources of colour may be present in the same petal, 

 and even in the same cell. The streaky colouring of Parrot Tulips 

 arises from the irregular distribution ot the chromoplasts m addition 

 tr) the soluble colouring. The outer floral envelopes take no direct 

 pari in propagalinn. Indirccth' thcv serve that purpose: the sepals 



244 



