INTRODUCTION TO CRYPTOGAMIC BOTANY. 443 



name from the crescent-shaped processes which produce the 

 gems, the involucres project horizontally in a cruciform manner 

 from the top of the stem when there are four, l^ut they occa- 

 sionally vary in number from five to six. The male fruit is con- 



Fig. 93. 



a. Plagiochasma mexicanum, receptacle, magnified. From a specimen 

 gathered by Salle at Cordova. 



b. Spore of ditto, seen from beneath. 



c. Part of mai-gin, more highly magnified. 



d. Stem with involucres and sporangia of Lximilaria vidgaris. From 

 Portugal, gathered by Welwitsch, 



e. Young involucres taken from an unexpanded bud, with one of the 

 basal scales reflected.* 



tained in sessile receptacles situated at the lobes of the frond? 

 which is porous as in Marchantia. The common stem bursts 

 through the frond, and has a little membranous cup attached 

 at the base, within this another cup, and within this, again, 

 several scales. 



* The tissue taken from these young sporangia contained in the invo- 

 lucres, resembles closely that of Marchantia (Fig. 92, e), except perhaps 

 that the mother cells are more disposed to divide lougitudimdly. 



