12 Britton and Taylor : Life History of Schizaea pusilla 



m 



(Fig. 76). The roots are fully formed and have root caps (Fig. 

 75, d). This root cap (Fig. 76) consists of four large pear-shaped 

 cells, inflated on one side ; the inflated side is away from the root, 

 the concave side rests on the root tip. They are developed before 

 the root sheath splits. The cells are replaced frc 

 the older ones do not always fall off when the new ones have been 

 formed, there have been seen as many as five series (Fig. J7), 

 though they show their age by the partial discoloration of their 



walls. 



The epidermal cells are large and thin-walled ; the outer walls 

 often bend into the cavity of the cell and frequently break. The 

 cortex consists of two layers ; the cells of the inner layer are very 

 large and have the walls that lie next to the endodermis thickened ; 

 but in no instance was the thickening found to be as great as that 

 figured for Schizaea Pennida. There is an endodermis of two 

 layers, and the central cylinder (Fig. 78) is like that described by 

 Prantl (Untersuch. Morph. Gefasskrypt, pi. 4.) for Schizaea Pennula. 



Sclerosis takes place in all the layers without any marked in- 

 crease in the thickness of the walls. 



Rhizome 



The rhizome is erect (Fig. 79), occasionally creeping. It always 

 forms a protective covering of trichomes over the growing end 

 (Fig. 74, d)\ these trichomes consist of from two to five cells 

 (Fig. 75, //), measuring 1 mm. in length which soon turn brown 

 and are persistent. The internodes are of varying lengths. One 

 rootstock (8 mm.) had borne nineteen sterile and two sporophylls, 

 all dead except the five sterile leaves last formed. The fertile 

 leaves measured 6.5 cm., the longest sterile leaf 4.5 cm. Another 

 rhizome of the same length had twenty-two sterile leaves, six 

 green and two nearly brown, with two fertile ; these were 7 cm. 

 high, the base of the fertile leaves was green, the sporangia brown 

 and mature. There were twenty -two roots — six short and young ; 

 one root was 25 mm. long and had branched; the branches were 

 5 mm. long. 



A cross-section near the young tip shows a central bundle with 

 a well developed endodermis (Fig. 80). Sclerosis takes place in 

 the entire cortex ; the different stages are beautifully shown in 



