34 INTRODUCTORY. PLANTS AND ANIMALS 



B. Types of the Plant Kingdom. 



A series of specimens will be given out by the demonstrators 

 to be handed round. These illustrate types of all the great 

 groups of the plant kingdom, from the highest (flowering) plants. 

 Ask the demonstrator any questions that occur to you about 

 them. 



Examine also the fully labelled demonstration series. 



C. Differences between Species of the Same Genus. 



Examine carefully fresh specimens of two or three species 

 of flowering plant belonging to the same genus. Write down the 

 differences which strike you, and get the demonstrator to correct 

 your notes and to point out the characteristic differences in case 

 you have failed to observe them. [The species used must depend 

 upon the time of year and upon what can be obtained. In 

 the autumn Quercus robur, Q. sessiliflora and Q. ilex are suitable ; 

 in April Veronica agrestis, V. hederifoUa and V. tournefortii ; 

 in May or June Ranunculus acer, R. repens and R. btilbosus.] 



D. Exceptions to the Characteristic Forms and Structures 

 OF Plants and Animals. 



{Demonstration Specimens.) 



(i) A Branching Animal- — Fresh or museum specimens of a 

 hydroid polyp or a bryozoon " colony." Each individual has a 

 mouth surrounded by tentacles and a gut. It consumes solid 

 food consisting of tiny organisms living in the sea, and is therefore 

 an animal in spite of the facts that it is fixed to one spot and 

 that the whole " colony " has a branching form like a plant. 



(2) A Compact Plant. — Mamillaria, or other cactus from 

 subtropical America, shows no obvious division of its shoot 

 into stem and leaves. It has a branching root in the soil like 

 an ordinary plant, but its shoot consists of a compact fleshy 

 green stem bearing spines or bristles which represent the leaves. 

 The compact form decreases the evaporating surface and at the 

 same time stores water which is held by the abundant mucilage 

 the plant contains, so that the cactus is able to live in a hot, dry 

 cUmate. 



(3) An Animal with no Mouth. — The tapeworm is a parasitic 

 animal which absorbs its liquid organic food from the intestines 

 of the animal in which it lives. It has no mouth or gut, having 

 lost these by degeneration in correspondence with its habit of 

 life. 



