10 OF THE ALG.E GENERALLY. 



the plants, and turns them yellow or brown ; but even 

 that is to be preferred to losing them altogether. At 

 the same time the collector should not forget to note the 

 fact of their having been immersed in alcohol, otherwise, 

 if exchanges are made, strange mistakes may arise as 

 to the original colour of the specimen. 



As may be supposed, plants which have grown in swiftly 

 flowing streams are more liable to decay after they have 

 been gathered, than those whose home is the stagnant 

 pond or marsh, since the conditions of life in the latter are 

 not so much interfered with by their removal ; indeed, they 

 will often continue to live and vegetate in a room, provided 

 attention be paid to the chemical quality of the water in 

 which they are found. 



As this little work is intended for the collector and not 

 for the systematist, nothing will here be said with regard 

 to the genera into which the Algae have been divided. 

 That portion of their history must be sought for in other 

 works, though of course in this, as in every other depart- 

 ment of Natural History, an intimate knowledge of both 

 genera and species is essential to the student. But, for 

 convenience sake and to avoid repetitions, we will, in the 

 following pages, confine our treatment of the subject to 

 certain heads, corresponding in some degree to the natural 

 divisions of systematic authors. 



[Having given on a preceding page one or two examples 

 of the lovely patterns which distinguish some of the fila- 

 mentous Algse, it will not be amiss to insert here some 

 specimens of the families of Diatomacese and Desmidiaceae. 

 The figures will assist the young student in discriminating 

 the members of these minute, but important, divisions of 

 the vegetable kingdom ; they will also help to point out to 

 him what wonderful treasures lie within his grasp, ready to 

 be seized as soon as his eye and hand are sufficiently 

 educated to make them his own. In the accompanying 

 Plates (n. in. iv. v.) the DiatomaceaB are represented by 

 figures 9 to 14, the Desniidiaceae by figs. 15 to 23. — Ed.] 



