154 PRINCIPLES OF BOTANY, &c. 
SCHREBER, in the last edition of the Genera Plan- 
tarum, has changed the Orders of the 24th class, as 
follows : 
1, Miscellanez. 
2. Filices. 
3. Musci. 
4, Hepatic. 
5. Algae. 
6. Fungi. 
It-would be superfluous here to take notice of 
other alterations which do not tend to the improve- 
ment of the science. 
§ 143, 
Besides the knowledge of different eens! it is 
very useful for a beginner to have some idea of the 
natural affinities of plants. He is thus, in the in- — 
vestigation of unknown plants, more easily led into 
the right track. We are indeed far behind in this 
branch of knowledge, and the little we know is 
very imperfect : but that little may be of great assist- 
ance to us in the investigation of plants, because bo- 
tanists in their descriptions often make use of ex- 
pressions by which plants of particular allied fa- 
milies are ascertained. Linnzeus has left us the fol- 
lowing arrangement of Natural Orden 
1. Raley S22. « 
2. Piperita. The flowers of this order are crowded 
into a close spike, as Piper, Arum, &c. 
3. Calmaria. To this. order belong all the 
Grass-like plants, which differ from the true Grasses 
by 
