ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 393 



the cavity being gradually formed, at first indistinct, but finally 

 assuming a nearly regular oval sbape. The protoplasm soon breaks 

 up into small round bodies which are discharged as antherozoids. The 

 first antheridia are formed singly ; but later two or three are formed 

 almost simultaneously at the end of a single branch. When the 

 antherozoids are mature, the cells surrounding the interior cavity of 

 the antheridium separate, leaving an opening by which they escape. 

 Usually the whole mass of antherozoids is discharged in a few minutes, 

 but sometimes the discharge is more gradual. Each antherozoid is 

 inclosed in, and lies coiled up within, a membrane. After resting for 

 a few moments this sac bursts, freeing the inclosed antherozoid, which 

 immediately swims rapidly away, with a peculiar undulatory move- 

 ment due to its spiral form. The antherozoids are of comparatively 

 very large size. The body is long and slender, tapering to a point 

 at one end, and bearing the remains of the enveloping sac on the 

 inner side. They are quickly killed by iodine ; the cilia becoming 

 rigid, and standing out in all directions from the thicker end of the 

 antherozoid. 



Reproductive Organs of Pilularia.* — K. Goebel has examined 

 the development and structure of the fructification of Pilularia 

 glohulifera. 



A longitudinal section of the young fructification shows that the 

 chambers in which the sporangia are formed are not closed, but have 

 an opening at the apex. The chambers are therefore not of endo- 

 genous origin, but are merely depressions in the surface. A placenta 

 springs from the outer wall of each chamber in the form of a cushion 

 ascending from below upwards, on which the sporangia are developed, 

 usually in ascending succession. The placentae are therefore, as in 

 Marattiacese, also products of superficial cells. 



The four projecting ridges which correspond to the four chambers 

 do not meet in the centre of the fructification, but are separated by a 

 moderately large mass of tissue, which, when the fructification is ripe, 

 separates into four sections. Goebel does not agree with Juranyi in 

 regarding these projections as tips of leaf-segments, but simply as 

 outgrowths of the outer margin of the four pits in which the sporangia 

 are formed. The entire fructification of Pilularia is, according to 

 this view, a simple leaf-segment, in depressions of which the sori are 

 developed, as in the homosporous Filicinese. The central mass of 

 tissue which separates the pits from one another does not at first 

 present any differentiation into four pits. This view of the structure 

 of Pilularia is confirmed by a comparison with Marsilea. 



The idea that the fructification of Pilularia is composed of four 

 leaf-segments has originated from the structure of the mature organ, 

 V(rhich splits into four parts. But this results from the central tissue 

 betw^een each pair of soral chambers splitting into two. In the centre 

 of the fructification is often a cavity caused by the violent ruptui-e of 

 the tissue ; but this was always occupied originally by starch-con- 

 taining tissue. The lines where the rupture subsequently takes place 



* Bot. Ztg., xl. (1882) pp. 771-8 (I pi.). 



