140 TYPE STUDIES 



4. The spore fruits (sporocarps) borne in groups on short 

 stalks, attached to the base of the leaf. The spore fruits 

 are modified portions of leaves, which are consequently 

 highly specialized sporophylls. 



Illustrate these features of the general morphology in a 

 habit sketch. 



B. The spore fruit, or sporocarp. Spore fruits of Marsilia ves- 

 tita open more readily in water and are generally more 

 favorable for this study than those of M. quadrifolia. Chip 

 the edge of a spore fruit with the point of a heavy knife 

 and place in water. It will probably open in an hour or 

 more, splitting along one side like a pod. Note : 



1. The emergence of a worm-like gelatinous structure bear- 

 ing elliptical spore masses, which are really groups of 

 sporangia and consequently sorl. Make a drawing to show 

 their appearance after emerging from the spore case. 

 Split a dry spore fruit lengthwise and observe the manner 

 in which the sori are arranged within. Illustrate. 



2. Examine a sorus under l.p. Note the two sizes of spores, 

 the larger called megaspo7'es and the smaller microspores. 

 Show their arrangement in the sorus. 



3. If the spore fruit has not been in the water too long, the 

 microspores will be found in groups of sixty -four, held 

 within a very delicate tissue which represents a microspo- 

 rangium. In this connection it is important to remember 

 that the common ferns produce sixty-four spores in their 

 sporangia. 



C. The microspores and tnegaspores. 



1. Draw the two forms of spores side by side to show com- 

 parative size. Note the slight protuberance at one end of 

 the megaspore. 



2. Crush the megaspore and stain the contents with iodine. 

 What are the large grains ? 



The spores begin to germinate at once, and after eighteen or 

 twenty hours develop small gametophytes of two forms : (1) male 



