CARPOSPOREM. 287 



spherical cushion ; the cellular filaments which are the result of germination branch 

 somewhat irregularly in one plane, but form something like a disc ; from them rise 

 up ascending articulated branches, which again branch and form the cushion. In the 

 following species no ascending branches are formed, but those which cling to their 

 support form a more or less regular disc. In C. irregularis this takes place by irregular 

 ramifications which lie in one plane gradually filling up all the interstices, till an almost 

 uninterrupted layer of cells is obtained. In C. soluta (Fig. 186), on the other hand, 

 a dichotomous ramification commences in the two first daughter-cells of the germinating 

 spore, with corresponding cell-division of such a nature that even at a very early 

 period a closed disc of radial forked branches is formed, which either lie loosely or are 

 closely crowded side by side. While in the species already named the branches arise 

 laterally from cells, but never from the terminal cell of a branch, in C. soluta we have the 

 first instance of dichotomy as well as regular disc-shaped centrifugal growth, a condition 

 which attains the highest development in C. scutata. In this species the cells which 

 result from germination remain from the first united laterally and do not form isolated 

 branches ; the circular disc, when once formed, continues to grow by increase of its 

 circumference, the marginal cells dividing by radial and tangential walls. This mode 

 of growth may be explained in this way, that the first branches are united laterally 

 and grow with equal rapidity in a radial direction, and then become divided by septa 

 (in this case tangential) ; while the broadening of the terminal cell of each radial row 

 corresponds with the succeeding radial division of a dichotomy. The law which prevails 

 in the species previously mentioned, that only the terminal cell of a branch is divided by 

 transverse septa, is exemplified in C. scutata by the marginal cells only of the disc being 

 divided by tangential walls. 



The Reproduction of the Goleochaeteae is brought about by asexual zoogonidia and 

 by resting oospores produced sexually. The oospores do not at once produce new 

 plants, but several zoospores ; and the following alternation of generations takes 

 place: — The zoospores, which arise in the early part of the year at the commence- 

 ment of vegetation from a sporocarp of the previous year, produce only asexual 

 plants, or, in other words, only such as can form zoogonidia. Only after a series of 

 asexual generations varying in length does a sexual generation arise, which may be 

 either monoecious or dioecious according to the species. Fertilisation produces one 

 oospore in the carpogonia, which clothe themselves with a peculiar layer of cortical 

 cells; and this oospore itself again developes into a parenchymatous reproductive 

 body, from the cells of which the zoospores proceed in the next period of vegetation 

 (Pringsheim). The zoogonidia (Fig. 187, D) may arise in all the vegetative cells of the 

 Coleochaeteae ; in C. pul'vinata especially from the terminal cells of the branches ; they 

 are always formed from the entire contents of the mother-cell, and escape through 

 a round hole in its cell-wall. 



The carpogonium is always the terminal cell of a branch, and hence in C. scutata 

 the terminal-cell of a radial row (Nageli). The peculiar mode of its development is 

 subject, according to the growth of the plant, to some, though subordinate, modifi- 

 cations. One species, C. pul'vinata (Fig. 187), may first of all be examined somewhat 

 more closely. The terminal cell of a branch swells up and at the same time elongates 

 into a narrow sac (Fig. 187, A, og, to the left), which then opens {og", to the right) and 

 exudes a colourless mucilage. The protoplasm of the swollen part, which contains 

 chlorophyll, forms the oosphere in which a nucleus is visible. The antheridia are formed 

 at the same time in adjoining cells, two or three protuberances {A, an) growing out, 

 which become separated by septa ; each of the cells thus formed, which have somewhat 

 the shape of a flask, is an antheridium ; its entire contents form an antherozoid (2) of 

 oval shape with two cilia which is endowed with motion like a zoogonidium ; its entrance 

 into the oogonium has not yet been observed. The effect of fertilisation is seen in 

 that the contents of the carpogonium become surrounded with a proper membrane and 

 form the oospore. This now grows considerably, and at the same time the formation of 



