Lecture XXVI. 231 



held in special protoplasmic bodies, the chromatophores, in the 

 cells. They are narrow at their base, by which they are attached 

 to the axis, and their distil end is expanded. There is usually 

 a curved indentation on their rounded outer end. Just at the 

 base on the upper surface there is a minute pocket formed by a 

 scale attached to the petal, with its opening directed upwards. 

 The inside of the pocket is moistened with a sugary, viscid juice. 

 Veins may be seen ramifying through the petals just as they are 

 visible in the foliage leaves. 



Above the whorl of petals a large number of filiform organs are 

 attached to the sloping side of the conical axis. These are the 

 stamens. Their points of attachment are arranged in spiral lines 

 upon the axis. Each stamen is formed of a tapering white stalk, 

 the filament, bearing at its top an ovoid enlargement, the anther, 

 yellow in colour and with a deep longitudinal groove. On each 

 side of this groove is a bulging mass, the anther-lobe. When the 

 stamen is mature each anther -lobe splits or dehisces longitudinally 

 and emits a yellow powder, the pollen. 



The origin of a stamen is similar to that of a foliage-leaf. It 

 begins as a small rounded excrescence on the side of the axis 

 formed of undifferentiated cells. Gradually the distal part of the 

 excrescence enlarges and the beginnings of the filament and anther 

 may be discerned. In the anther a shallow, longitudinal groove 

 appears dividing it into two lobes. The growth of the tissue 

 forming the bottom of the groove widens it and separates the two 

 anther-lobes. This tissue is called the connective. In the con- 

 nective and filament a small conducting tract is developed which 

 makes connection with the conducting tracts of the axis. In each 

 anther-lobe two columns of cells differentiate. The cells forming 

 them are distinguished from their neighbours by their larger 

 nuclei, more granular contents and larger size. Round each 

 column is a layer of crushed cells called the tapetum. The columns 

 are called the archesporia and give rise to the spores or pollen - 

 grains. The component cells are the pollen-mother-cells, which 

 are similar in their characteristics to the pollen-mother-cells of the 

 Pine and the spore-mother-cells of the Archegoniatae. As the 

 archesporia increase in size they come. to occupy more and more 

 of the anther-lobes so that the sterile tissue of each anther-lobe 

 separating its two archesporia becomes a narrow partition. The 

 nuclei of the pollen-mother-cells divide twice and so give rise to 

 four nuclei, tetrahedrally arranged in each cell. The cytoplasm 

 segments to form round each of these nuclei a globular mass. 

 This develops a cell-wall, the outer surface of which is roughened 



