Introductory. 13 
10. Hardiness and Tenderness are terms used to ex- 
press the power possessed by different plants or animals to 
endure extremes in their environment. The Oldenburgh 
apple endures without material harm vicissitudes of tem- 
perature that are fatal to many other varieties; in other 
words, it is hardier as regards temperature, than many 
other varieties. The reindeer is hardier as regards cold than 
the elephant, but tenderer as regards heat. The melon plant 
is hardier as regards heat and drought than the lettuce, but 
tenderer as regards wet or cold. 
11. Health and Disease. A plant or animal is said 
to be in health when all its organs (parts) are capable of per- 
forming their normal functions. An organ incapable of 
doing this, or the being possessing such an organ. is said to 
be diseased. 
12. The Cellular Structure of Living Beings. A 
bit of vegetable or animal substance, examined under a 
microscope of moderately high power, is seen to be made up 
of numerous little sacks or cav- 
B ities, more or less clearly de- 
fined, called cells. Cells from 
different beings, or from differ- 
D ent parts of the same being, 
@) EB G may vary much in form and 
OO size, but they are seldom large 
Fie. 1. Showing four individual enough to be seen without mag- 
plants of a species of Protoccus. A ea 
shows a plant before commencing ifying power. Some of the 
to divide into other plants. B. C. S 
and D show how the cells divide to lowest plints and animals con 
form other plants. Highly magni- sist of single cells (Fig. 1). 
fied a 
. Some of the lower plants con- 
sist of a single row of cells united at the ends (Fig. 2). 
