RHIZOCARPE.E. 



385 



divisions at right angles to one another ; each of the latter is divided into four 

 portions disposed tetrahedrally. The 32 smaller primordial cells which are formed" 

 in this manner became surrounded with thin cell-walls, and are the mother-cells of 

 the antherozoids (Hanstein). This cellular body which produces the antherozoids 

 is called by jMillardet the Antheridium, since he considers the space between it and 

 the endospore filled with sap (in which at first a number of starch-granules lie) as a 

 rudimentary indication of a male prothallium, a view which, although it sounds 

 singular, appears confirmed by the behaviour of the microspores of Isoetes and 

 Selaginella. As in Ferns, we find also in Rhizocarps only a portion of the con- 

 tents of the mother-cell applied to the formation of the antherozoid. According to 

 Millardet^ this portion assumes the form of a roundish turbid lump consisting of 

 protoplasm and starch-granules, which, during the formation of the antherozoids, 

 becomes gradually clearer, and, when the latter escape from the mother-cell, forms a 

 vesicle consisting of the unused protoplasm and the starch-granules lying in it. In 

 Pilularia, where the antherozoid is a thread coiled four or five times, this vesicle 

 remains attached to the mother-cell. In INIarsilea, on the contrary, it adheres to 

 the posterior coils of the corkscrew-like antherozoid, which is coiled 12 or 13 times; 

 and is often carried about with it for a considerable time by its swarming motion, 

 but finally becomes detached. When the antherozoids are formed in their mother- 

 cells, the exospore bursts at the apex, the endospore swells up as a hyaline bladder, 

 which finally bursts and allows the escape of the antherozoids (Fig. 286, B). 



The Female Prothallium is formed within the apical papilla of the macrospore 

 from a small part of its protoplasm, and only partially emerges at a later period 

 from the spore-cavity, but remains united with the latter, closing it by its basal 

 surface, for the purpose of using up the food-materials (starch-grains, fatty oil, 

 and albuminous substances) which are stored up there. The separate stages in 

 the first formation of the prothallium are still in many respects not clear; but it is 

 certain that it arises from a collection of protoplasm in the cavity of the papilla ; 

 this protoplasm immediately breaks up into several cells, which, according to 

 Hanstein (in IMarsilea and Pilularia) become clothed only at a later period with 

 cell-walls and thus form a tissue. The further processes seem to me, according to 

 the statements of Pringsheim, Hanstein, and Hofmeister, compared with my own 

 observations on Marsilea salvairix, to be briefly :— the tissue of the prothallium is 

 for a certain time completely enclosed in the apical papilla of the macrospore, 

 covered above by the epidermal layers of the apex of the spore itself, and shut 

 oflf from the spore-cavity below by a lamella of cellulose which is stretched across" 

 like a diaphragm and is attached at the circumference to the endospore. By the 

 further growth of the prothallium the epidermal layers of the papilla are ruptured 

 above, the dorsal part of the prothallium projects into the funnel-shaped cavity 

 which is left by the absence of the thick epidermal layers of the macrospore ; 

 subsequently the diaphragm arches convexly, and the prothallium is thus pushed 

 further outwards. This is the present state of our knowledge with respect to the 

 position of the prothallium in the macrospore. (Compare the explanations of the 

 figures further on). 



» For the different view adopted by Hanstein, vide I c 

 C C 



