Britton and Taylor : Life History of Schizaea pusilla 15 



gin produce trichomes which also cover the sporangia. These 

 trichomes are often composed of more than one cell, and resemble 

 the trichomes formed by the rhizome and are in some instances as 

 long as 134 /i, 345 /i, 461 ix, the width being 38 jx, and 30 }x. 



A surface view of the dorsal side of the sporophyll shows two 

 rows of stomata alternating in some cases with rows of glands, 

 though these sometimes are not in rows, and occasionally only 

 two glands were found. These glands are smaller than those 

 generally found on the sterile leaf measuring only 38 fi. 



The stomata appear sunk below the epidermis, but a cross-section 

 showed them to be the same as in the sterile leaf. The two rows 

 of stomata continue up the leaf from the base to the pinnae, where 

 they are lost in a great number of stomata which cover the dorsal 

 surface of the pinnae with no special arrangement. No glands 

 were found on any of the pinnae examined. 



The warts or swellings from the epidermal cells are far more 

 numerous in the sporophyll, though they are found on the sterile 

 leaf (Fig. 93, a). They do not appear to follow any law as to their 

 arrangement on either leaf, though they appeared to be more 

 numerous on the ventral side. The epidermal walls are thicker 

 than the epidermal walls of the sterile leaf, some of which had ex- 

 tremely thin walls and a rudimentary bundle (Fig. 90). 



The bundle has a well-marked endodermis ; it appeared from the 

 cross-section to be collateral as did all the bundles with the excep- 

 tion of that of the rhizome (Fig. 94). The elements of the bundle 

 were not traced out, but reticulated and ring tracheids were 

 found in the xylem. The mesophyll tissue of the sporophyll (Fig. 

 89) is composed of thin-walled cells with numerous air spaces : 

 these cells seem to be branched in a stellate manner in both sterile 

 leaves and sporophylls. 



Summary 



The spores are small, are nearly reniform, and have a cuticu- 

 larized exospore which is alveolate. There is a ridge along the 

 concave side having a fissure nearly its whole length through 

 which the young tube emerges when the spore germinates. 

 Out of a great number sown at one time only two had germi- 

 nated by the end of the third week, the others taking a longer 



