194 OF THE HERBARIUM. 



Should the genus be so extensive, as . to necessitate the 

 division of the species into sections, it may be labelled and 

 catalogued after the following fashion. We will suppose 

 that the Diatomaceous genus Nitzschia is the 138th in the 

 system adopted by the student, and that he possesses the 

 species named below. 



138. Nitzschia, Hass. 



a. Frustules arcuate. 



1. N. amphioxys, W. Sm. 



b. Frustules constricted in the centre. 



1. N. plana, W. Sm. 



2. N. constricta, Pritch. 



3. N. parvula, W. Sm. 



4. N. latestriata, Breb. 



c. Frustules sigmoid. 



1. K sigmoidea, W. Sm. 



2. N. curvula, W. Sm. 



d. Frustules straight, linear, or lanceolate. 



1. N. tenuis, W. Sm. 



2. N. communis, Bab. 



3. N. hyalina, Greg. 



It will be observed, that the sections are marked by a 

 letter of the alphabet, and that each commences with number 

 ' one.' Care must be taken to leave sufficient space between 

 each section to allow of the insertion of fresh names. 



The herbarium is best preserved on the shelves of a 

 closet provided with well-fitting doors to exclude the dust, 

 and kept in a room in which a fire can be lit during the 

 winter, and in exceptionably damp weather. 



It is of no use, however, to take pains in preparing 

 specimens, labelling them correctly, and providing them 

 with shelves and drawers, unless the greatest care be taken 

 for their preservation afterwards. 



If the plants are liable to injury from damp or rough 

 usage, still more so are they from not being touched at all. 

 Neglect is worse than careless handling, or indeed than any 



