218 PRACTICAL LESSONS IN SCIENCE. 



posed of thin scales or bracts and thicker ones called carpellary 

 scales. Dissect out one of thicker scales and study its shape and 

 texture and compare it with the thinner bract. Note the promi- 

 nent ridge or keel on the upper surface and the two enlargements 

 near the base, the ovules. Notice the position of the ovules and 

 the opening at the free end called the micropyle. Note that the 

 cluster seems to take the place of a branch. 



Split a one year old cone and examine carefully all the parts 

 in section, notice the ovules, the abortive ovules, the scales, and 

 make a diagram showing the relation of the parts to each other. 

 Dissect out an ovule and bisect it through the micropyle, and 

 notice the nucleus, and a large cavity called the embryo sac, 

 enclosing a soft substance called the endosperm. 



In the mature cone notice the heavy carpellary scales, and the 

 smaller bracts, and along the inner surface of the scales will be 

 found a pair of thin wing-like scales, each bearing at its lower 

 end a seed or an abortive ovule. 



In the case of the seed, note its form, character of surface, 

 micropyle, etc. Bisect the seed lengthwise, parallel with its nat- 

 ter faces, and notice the firm outer coat, the embryo and the 

 food for the embryo, the endosperm. Carefully pick out the 

 embryo with needles and note the short stem, and the young 

 leaves. 



A study of the pine according to the foregoing scheme will give 

 one a good idea of the gross features of the pine family. The 

 careful study of one tree or plant is of great value even though 

 it may be far from complete. The scheme suggested may be va- 

 ried to suit individual ideas and opportunities. The idea has 

 been to encourage careful, systematic study, and to this end full 

 notes should be taken, and numerous drawings, diagrams and 

 sketches made and specimens gathered and preserved for reference 

 and study. 



The wood of the pine is composed mainly of tracheides, while 

 the bark is made of sieve tissue and bast fibers. The tree grows 

 from the cambium layer or meristem tissue lying between the 

 wood and the bark. The cells of this tissue undergo division by 



