igo ANCIENT PLANTS 



Morphology. The study of the features of plants, their shapes and 

 relations, and the theories regarding the origin of the organs. 



Nucellus. The tissue in a Gymnosperm seed in which the large 

 "spore" develops. See figs. 55 and 56, p. 76. 



Nucleus. The more compact mass of protoplasm in the centre of 

 each living cell, which controls its growth and division. See 

 fig. 17, n. 



Palaeobotany. The study of fossil plants. 



Palaeontology. The study of fossil organisms, both plants and 

 animals. 



Petiole. The stalk of a leaf, which attaches it to the stem. 



Phloem. Commonly called "bast". The elongated vessel-like cells 

 which conduct the manufactured food. See p. 57. 



Pollen Chamber. The cavity inside a Gymnosperm seed in which 

 the pollen grains rest for some time before giving out the male 

 cells which fertilize the egg-cell in the seed. See p. 76. 



Polystelic. A type of stem that appears, in any transverse section, 

 to contain several steles. See note on the use of the word 

 on p. 63. 



Protoplasm. The colourless, constantly moving mass of finely 

 granulated, jelly-like substance, which is the essentially living 

 part of both plants and animals. 



Rock. Used by a geologist for all kinds of earth layers. Clay, and 

 even gravel, are "rocks" in a geological sense. 



Roof, of a coal seam. The layers of rock usually shale, limestone, 

 or sandstone which lie just above the coal. See p. 24. 



Sclerenchyma. Cells with very thick walls, specially modified for 

 strengthening the tissues. See fig. 28, p. 56. 



Seed. Essentially consisting of a young embryo and the tissues round 

 it, which are enclosed in a double coat. See definition of " Fruit ". 



Shale. A fine-grained soft rock, formed of dried and pressed mud or 

 silt, which tends- to split into thin sheets, on the surface of which 

 fossils are often found. 



Species. Individuals which in all essentials are identical are said to 

 be of the same species. As there -are many variations which are 

 not essential, it is sometimes far from easy to draw the boundary 

 between actual species. The specific name omes after that of the 

 genus, e.g. Pinus montana is a species of the genus Pinus, as is 

 also Pinus sylvestris. See " Genus ". 



Sporangium. The saclike case which contains the spores. See figs. 

 52 and 53, p. 75. 



