May 1, 1SG6.J 



SCIENCE-GOSSIP. 



103 



is formed, called a sporangium, which is believed in 

 due time to produce a multitude of individual 

 spores, ultimately growing to Closteria. The opera- 

 tion of forming a sporangium is said to be very- 

 rapid, only occupying a few minutes. We have 

 never been fortunate enough to witness it. A 

 third mode of reproduction (in Cosmarium) is sus- 

 pected, and mentioned in Pritchard. To this book, 

 embodying the observations of a host of inquirers, 

 we refer the reader for the fullest information, up 

 to the present time, attainable. At most, however, 

 very little is known of the desmids, and if the 

 readers of Science Gossip will set to work, pro- 

 viding themselves with the home-made growing- 

 slides invented by Professor Smith, of Kenyon 

 College, U.S., or with Mr. Beck's improvement, 

 the results attained will repay them ; provided 

 they diligently search after truth, rather than ad- 

 vance speculations. The " Micrographic Diction- 

 ary" says, "No less than four modes (of repro- 

 duction in desmids) have been observed, and many 

 points connected with the subject still remain to 

 be cleared up." 



While we write we have under examination 

 several species of Closterium, which were gathered 

 at Keston, on the ISth December last, and have 

 been kept in a bottle ever since (two months), with- 

 out detriment.* We think the reader will readily 

 identify the forms figured. One of the largest and 

 most beautiful is C. lunula, the end only of which 

 we have drawn, because, on the same scale, it would 

 have filled our page entirely. 



Fig. 97. Euastrum oblongum (front view) x 250. 



Another kind of desmid introduces itself under 

 the name of Ernst rum. This is somewhat lozenge- 

 shaped (in front view), with rounded protuberances 

 or inflations, and thicker near the middle than at 

 the edges. The central division is strongly marked. 

 We figure examples of E. oblongum in different 

 positions, that some notion of the shape may be 

 obtained. The endochrome is of a beautiful herba- 

 ceous green, but then this colour is common to all 

 desmids, so we need hardly notice it. Occasionally 

 circulation may be seen in the interior, but not 

 often. There are many species of Euastrum, 



* Except such as have been eaten by various animalcules 

 and Crustacea; by no means an inconsiderable number. 



differing greatly from each other, both in size 

 and form. Once or twice I found a frond ex- 

 hibiting the swarming motion of the contained 

 atoms to which we shall refer presently, and which 

 appears to appertain to many other sorts as well 



Fig 1 . 99. Euastrum oblongum (side view and 

 end view) x 250. 



The, Micrasterias is a large and beautiful represen- 

 tative of the group. It is disc-shaped and flat, like 

 a pan-cake. The edges are nicked regularly all 

 round, as if with scissors, and the green contents 



I 





Fig. 99. Micrasterias rotata x 250. 



cease at a little distance from the margin, giving 

 the whole a most delicate appearance. We have 

 seen circulation in some specimens. The different 

 species of Micrasterias are numerous. 



1 1 ft* 



Fig. 100. Cosmarium margariti- 

 ferum x 250. 



Fig. 101. Cosmarium mar- 

 gnritiferum (empty 

 frond) x 250. 



The Cosmarium is a singularly pretty organism of 

 dumb-bell shape, having the surface covered with 

 warts, which in profile look like spines. When the 

 frond is empty, and many examples will be found, 

 the sides collapse slightly, and the warts appear as 



