PILITLARIA SPOROPHYTE 323 



packed, and with remarkably thickened and stratified 

 walls. 



c. Within these is a spongy parenchyma, with 

 large intercellular spaces, and much starch : concentric 

 vascular bundles are found here and there embedded 

 in it. 



d. The placentae, consisting of parenchyma, with a 

 large vascular bundle in the centre of each. 



e. The microsporangia, each consisting of a short 

 stalk, and an elongated pear-shaped head : the wall, 

 consisting of a single layer of cells, may be more or less 

 disorganized according to age, the cell-walls being 

 mucilaginous : the microspores are numerous, and 

 relatively small : their wall consists of an inner firm 

 layer, and an outer stratified, mucilaginous layer, which 

 swells largely with water. Centrally is an undivided 

 protoplasmic body. 



/. The macrosporangia have an outer wall con- 

 sisting of a single layer of cells, which closely invests 

 the single large macrospore : this has its apex 

 directed away from the placenta. Centrally is a large, 

 undivided protoplasmic body, with numerous large 

 starch-grains: this is surrounded by a massive wall, 

 in which four layers may be recognized : the inmost 

 layer is thin and brown : the next layer is also thin, 

 and projects as the apical papilla : the third layer forms 

 an incomplete covering of variable thickness, and very 

 marked prismatic structure : the fourth, also incomplete 

 at the apex, is a very wide mucilaginous band, showing 

 indications of striation and stratification. 



By cutting sporocarps of various ages taken earlier in the year, 

 the development of the sporangium may be found to coincide in 



Y 2 



