454 



BOTANY 



develops into an embryo l whose foot, remaining for a time sunk in the venter of 

 the archegonium, finally ruptures it (Fig. 418). The first leaf of the germ plant is 

 shield-shaped (Fig. 415 0). 



The development of Azotta ( 11S ) proceeds in a similar manner, but the sporangia 

 and spores exhibit a number of distinctive peculiarities. The numerous spores of 

 the microsporangia are aggregated into several nearly spherical balls or massulae, 

 formed from the interstitial substance derived from the protoplasm ot the 

 cells. Each massula, enclosing a number of spores, is beset externally with 



FlG. 417. Sttlrli'in ?;/.>. Development 

 of the male prothallium. A, Division 

 of thei microspore into three cells 

 /-/// ( x SCO) ; B, lateral view ; r. v.-n- 

 tral view ofi (mature prothallium '(< 

 640). Cell / has divided into the pro- 

 thallium cells n, and p ; cell //, into the 

 sterile cells l>, c, and the two cells' .j. 

 each of which has (bnBedltwotsfwnna- 

 tozoid mother-cells; cell 1 ///, into the 

 sterile cells d, e, and the two cells .-._,. 

 Tlie cells jt t sj ami 83*2 represent two 

 antheridia ; the cells ft, c, :</. e their 

 wall-cells. (After BELA.IEKF.) 



Kin. 41s. xf !'< IK i"itnn*. Embryo in longitudinal sec- 

 tion ; pr, prothallium ; X, spore-cell ; e, exinium 71, 

 perinium ; spw, sporangial wall ; ar, archegonium ; 

 tmbr, embryo ; /, foot ; MI, bl%, big. the lirst three 

 leaves : st. ap-x of stem. (After PRINCSHFIM. X 100.) 



hook-like outgrowths of the interstitial substance (glochidia). On the rupture 

 of the sporangia the massulse are set free in the water, and are carried to the 

 macrospores, to which they become attached. A sporocarp contains one macro- 

 sporangium, in which only a single macrospore comes to maturity ; in the course 

 of its development it supplants all the other sporogenous cells, and finally the 

 sporangial wall itself becomes flattened against the inner wall of the sporocarp, 

 frequently undergoing at the same time partial dissolution. The macrospore is 

 enveloped by a spongy perinium whose outer surface exhibits numerous depressions 

 and protuberances prolonged into filainents. At the apex of the spore the perinium 

 expands into three pear-shaped appendages, while the upper part of the ruptured 



