Thallophyta and Bryophyta 163 



eliminates the fruitless sectioning in paraffin ol many vegetative 

 thalli. Ihe developing sporophytes ot Riccia are visible within the 

 thallus, and \arious stages can be classified roughly by size. Remove 

 enough of the thallus with these organs to show some of the 

 envelojiing cells. Fruiting thalli of Anthoceros should be killed entire, 

 in a vacuum jar (Fig. 3.1) , and the sporophytes dissected away with 

 a section of thallus after hardening in the fluid for several days. Both 

 transverse and longittidinal sections of the sporophyte should be 

 made. 



The leafy liverworts are easily overlooked on collecting trips, and 

 therefore do not receive adecjuate attention. Pellia and Porella are 

 most commonly used to illustrate this group. They can be processed 

 like the mosses as outlined below. 



Musci 



These plants are readily obtainable in fresh condition during the 

 greater part of the year in all but the most severe climates, and they 

 can be grown easily. They make usable dried specimens and can be 

 preserved in excellent condition in the fluids given in Chap. 10. 

 Gemmae, fidly developed sex organs, and most featm-es of the capsule 

 can be studied from dissections. Prepared slides are needed principally 

 for studying young sex organs, gametes, and some features of the 

 developing sporophyte. 



For the study of sex organs the large and more common species of 

 Mnium, Polytrichum, and Rhodobryitm are recommended. The 

 proper killing fluid for sex organs and gemmae of mosses and leafy 

 liverworts can be determined quickly. Obtain fresh turgid plants, 

 dissect out a few short pieces of the shoot bearing the sex organs, and 

 immerse in the fluid that is to be tried. Exhaust the air that adheres 

 tenaciously among the leaves. After 1 hr. in the killing fluid dissect 

 out a few gametangia, mount in a drop of the fluid, and examine with 

 a microscope under at least 400X- If plasmolysis has occurred, adjust 

 the formula. It is a good practice to try FAA and FPA (page 15) . If 

 these cause excessive shrinkage, try Craf I, an excellent formula. 

 Adjustments in this formula are made by increasing the ratio of acid 

 until no marked plasmolysis occurs. Use the stains recommended for 

 liverworts. 



Capsules of mosses are a vexingly difficult subject. Young green 

 capsules of Mnium cuspidatiim and Funaria hygyometrica are 

 penetrated by Craf I, but for older, coloring capsules, FAA or FPA 

 must be used. However, the interesting stages of sporogenesis take 



