246 W. HOFMEISTEB ON THE DEVELOPMENT OF ZOSTERA. 



greatly strengthened, the other weakened, sometimes even so 

 far as to disappear. It is not improbable that the different 

 temperatures of the ends of the filiform cell form one of the 

 causes on which the phaenomena of motion of the granular 

 mucilage are dependent. 



The investigation of the development of the pollen of Zostera 

 is very difficult. The contents of the cells of the young anther, 

 especially those of parent-cells of the pollen-cells, and of the 

 latter themselves, are extremely sensitive to the action of pure 

 water. This holds in a still higher degree of the pellicle form- 

 ing the coat of the young pollen. When an available preparation, 

 a very delicate longitudinal section of a young half-anther, is 

 placed under water, the membranes of the young pollen-cells 

 swell up, and, with their mucilaginous contents, instantly run 

 together into a shapeless jelly. The only method of examining 

 the young anther is to place it in a saline solution ; I employed 

 here, as in similar cases, a saturated solution of carbonate of 

 ammonia. No safe conclusions can be obtained regarding the 

 structure of the anther, or the course of development of the 

 pollen, without making sections. The connection of the different 

 tissues is so intimate in the young anther, that it is quite im- 

 possible to extract uninjured either the parent-cells of the pollen 

 or the very young pollen- cells*. 



The first visible rudiment of the ovary is a flat papilla (fig. 3 b) 9 

 composed of few 7 cells, which, increasing in size, soon acquires 

 the form of a horse-shoe with the convex side turned towards 

 the median line of the inflorescence (fig. 4 b), the rudiment of a 

 leaf attached upon the surface of the spadix. In a short time, this 

 becomes closed in so as to form an annular wall of cellular 

 tissue, within which appears a little roundish mass of cellular 

 tissue (fig. 160), approached near to the inner border; this is 

 the axillary bud of the carpel the ovule. The circular wall 

 becomes developed particularly quickly on the side next the 

 base of the spadix. It bulges out at this place, while it grows 



* The globular cells which Gronland mentions as the contents of the loculi 

 of the young anthers, and likewise figures (loc. clt. p. 188, figs. 18, 19, 20), 

 I was unable to find, at any stage of development of the anther. The closely 

 packed, straight and parallel pollen-cells always completely filled up the cavity 

 of the anther. Probably those appearances depended on some of the cells of the 

 lax and mucilaginous innermost layer of the wall of the anther being accidentally 

 detached in the preparation of the object. 



