226 Methods in Plant Histology 



Sporangia. All the sporangia of the plant may be said to con- 

 stitute a single strobilus of the Selago type. Both longitudinal and 

 transverse sections should be cut. The stem is so short that, in 

 a plant of medium size, a longitudinal section may include the stem, 

 the sporangium, and the sporophyll, up to the top of the ligule. 

 Such sections, 10 to 15 /z, or even 20 JJL in thickness, are best for 

 demonstration. For very detailed work, the older sporophylls 

 should be removed separately, taking a piece from the top of the 

 stem to the tip of the ligule. Transverse sections through the whole 

 cluster of sporophylls show the arrangement of megasporophylls 

 and microsporophylls and also the relations of the sporangia to 

 sporophylls. We have seen long, even ribbons through a group of 

 old sporophylls 2.5 cm. in diameter cut with a Gillette blade in 

 a Strickler's holder. 



The gametophytes- -The spores are shed in the uninucleate stage, 

 and consequently it is not so easy to find the germination as in the 

 case of Selaginella. When the large megasporangium begins to 

 decay, let the megaspores dry naturally. They retain their power 

 of germination for a year at least. Simply wet them with tap water 

 and the earlier stages are easily secured, quite clean and ready for 

 cutting. There must be soil in the dish for later stages. Try a 

 similar method for microspores. Also, look at the top of the stem 

 of old plants for stages developing naturally. The cell walls of the 

 male gametophyte, as in the case of Selaginella, are rather hard to 

 differentiate. Use anilin blue or light green. 



