276 



METHODS IN PLANT HISTOLOGY 



Spores of Marchantia polymorpha germinate as soon as they are 

 shed, but can be kept about a year in envelopes at room temperature. 

 The young sporehngs, looking hke young fern prothallia, are very 

 small. It is convenient to grow them on porcelain plates kept moist 

 with Knop's solution under a glass bell jar. 



If even a small room in a greenhouse is available, liverworts can be 

 grown in great variety and abundance. On one side of the room, have 

 a pile of rocks. Half of this space should be occupied by limestone 



rocks, held in place with as little 

 mortar as possible. There should 

 be some shale and some porous red 

 brick. The whole should be ar- 

 ranged so that water may trickle 

 down from above. A pipe with 

 holes iV inch in diameter will fur- 

 nish enough water. The other 

 three sides may be built up of va- 

 rious rocks, and some clay, so as to 

 form a table about 1 m. high. A 

 small fountain, with a bowl a 

 couple of feet in diameter, built of 

 rocks, will add to the efficiency. 

 If a few well-supported cement 

 tanks be placed above the princi- 

 pal pile of rocks, Isoetes and all the water ferns may be grown there, 

 besides Elodea, Myriophyllum, Chara, and other forms constantly 

 needed in laboratory work. 



The thallus. — Young stages in the thallus are usually neglected. 

 They should receive much more attention from advanced classes. 

 Spores of many liverworts germinate so readily that there is no diffi- 

 culty in getting material. Marchantia is so universally used for adult 

 stages of the thallus that a study of its early stages is very appropriate 

 (Fig. 76). 



For the adult thallus in many cases it will not be necessary to make 

 a special preparation for the study of the thallus, since preparations of 

 antheridia, archegonia, or sporophytes may include good sections of 

 vegetative portions. This is particularly true of forms hke Riccia, 

 where the various organs are not raised above the thallus. In forms 

 like Marchantia, where the antheridia, archegonia, and sporophytes 



Fig. 76. — Marchantia polymorpha, early stages, 

 looking like fern prothallia. From spores ger- 

 minated on porcelain plates. A and B X150; 

 C X 100. After Sister Mary Ellen O'Hanlon. 



