INTRODUCTION. 7 



In case good mounts are obtained and there is not 

 time sufficient to complete the study before the close of the 

 laboratory period, they may be preserved by replacing the 

 water of the mount by use of a ten per cent solution of 

 glycerin in water. A liberal supply of the solution should 

 be used, since the water evaporates, thus causing a thick- 

 ening of the glycerin. Mounts so made may be preserved 

 for weeks. When the glycerin has become quite thick 

 these mounts may be made permanent by "ringing" 

 them with cement. To do this first remove the glycerin 

 from about the edge of the cover-slip by use of a cloth 

 dampened in alcohol; then place the slide on the turn- 

 table, and after having put it in motion, apply tangentially 

 to the margin of the cover-slip, by means of a camel's- 



the student who expects to do such work should consult Chamberlain's 

 "Methods in Plant Histology" and numerous articles in the "Journal 

 of Applied Microscopy." Specific references will be made later. 



Unless the class is to do considerable work in histological technique 

 the laboratory should have ready for use a set of good slides of the 

 more difficult sections called for in the outline. Sections of the follow- 

 ing things should be included, and many others may be added with profit: 



1. The host plant of the parasite Albugo, illustrating the structure and 

 reproduction of the latter. 



2. The gametophyte of Riccia, showing vegetative structure, sex-organs, 

 and young sporophyte. 



3. Marchantia, showing vegetative structure of thallus, archegonial 

 and antheridial heads, and stages in development of sporophyte. 



4. Anthoceros gametophyte and sporophyte. 



5. Porella branches bearing sex-organs and sporophytes. 



6. Moss, showing sex-organs and capsule. 



7. Pteris or a similar fern, showing leaf, rhizome, sporangia, gameto- 

 phytes with sex-organs, and young sporophytes. 



8. Marsilia or Selaginella, showing structures of male and female 

 gametophytes. 



9. Pine, showing wood, needle-leaf, microsporangia, megasporangia, 

 with gametophytes, and young sporophytes. 



10. Trillium leaf, root (or onion root), stem, microsporangia, and 

 megasporangia . 



11. Ranunculus, microsporangia. megasporangia, and stem. Rumex 

 will serve as well. 



