QUEKETT MICEOSCOPICAL CLUB. 257 



round it. These enveloping cells eventually disappear and leave 

 a series of spiral ridges on the oospore, often flanged. The 

 stems and branchlets of the Nitelleae have single cells, while the 

 Chareae have a series of cortical cells surrounding the central 

 cells. N. cafillaris is a very rare species, only found in one 

 ditch in England. Its fruit is entirely surrounded by a trans- 

 parent gelatinous substance. Several other species are very rare, 

 but there seems to be no fear that collectors may exterminate 

 them, as it is impossible to drive out a charophyte that is 

 determined to stay, and equally impossible to keep one that is 

 determined to go. It is often very difficult to determine the 

 species of a charophyte, and microscopic characteristics have 

 to be relied upon. The mucro which terminates the branchlet is 

 sometimes of specific value. N. batrachosperma and N. tenuis- 

 sima are so much alike that it is almost impossible to dis- 

 tinguish them without a microscopical examination, a point of 

 difference being the decorations which are found on the membrane 

 of the oospore. The most interesting Nitellas are found in fresh- 

 water near the sea, which is always a likely place in which to 

 find them. The growth of the cortical cells of the Chareae 

 proceeds from the nodes of the stems and branchlets, and 

 they grow upwards and downwards along the stem until 

 they meet in the middle. A very curious appearance is 

 produced in C. denudata by the cortical cells being remarkably 

 undeveloped, and not reaching those which have started to 

 meet them. On the other hand, an Irish species of Chara 

 has very large cortical cells and large spine cells. C. fragifera, 

 which is found only at Land's End and the Lizard, has very 

 well-developed cortical cells and starch bulbils on the roots. 

 C. aspera has single spine cells, while C. desmacaniha has strongly 

 developed fasciculated spine cells. The fruits of the charo- 

 phytes are filled with starch and fat granules. When growth 

 begins the cells divide, forming the proembryo and the root ; 

 the proembryo has a node from which the sexual plant starts ; 

 accessory embryos also develop. The antheridium is one of the 

 most beautiful structures in the botanical world. It consists of 

 eight shields closely adpressed together. From the middle of 

 each a sort of handle, called the manubrium, projects inwards, 

 and at the end of this is a bunch of filaments. Each filament 

 consists of 100 to 200 cells, each of which contains an anthero- 



