7(3 ON THE DESMIDIACE.E. 



living sporangia contained eight or sixteen green daughter cells, 

 each of them discoid in outline, with a strongly marked central 

 notch. These daughter cells were finally set free by the solution of 

 the spore wall, as Cosmaria of minute size, but agreeing in all 

 other characters with the specific form to which they belonged. 



According to Braun, in the larger, more or less lunate Closteria, 

 conjugation occurs in the following method : Two fronds approach 

 one another in such a way that they lie back to back. In the 

 middle of each of them there then appears an annular line or trench 

 reaching through the cell wall, and accompanied by a distinct 

 separation of the endochrome into two halves. Whilst these 

 changes have been progressing there has also formed a new double 

 wall at the position of the trench, so that out of the two Closteria 

 two pairs of separate equal celts have been formed. Near to the 

 larger or central end of each of these now appears a pouting trans- 

 parent nipple like process. The corresponding opposing processes 

 enlarging and meeting coalesce, so that the upper half of one 

 Closterium, in the form of a daughter cell, is finally united with the 

 upper half of the other Closterium, and the two lower halves are also 

 joined together. Thus from a single pair of fronds arise two con- 

 jugating pairs of cells, and finally two sporangia, in each of which 

 a spore is perfected. 



This process does not seem, however, to be universal amongst the 

 Closteria, for in many, if not all, of the smaller species, a pair of 

 fronds produces a single sporangium. 



In the genus Palmoglcea, in which I have had an opportunity to 

 study the development of the spores, the process closely simulates 

 that seen in certain of the Spirogyra. The contents of the cells 

 first became broken up and confused, and almost simultaneously the 

 nucleus disappeared, the cells became swollen at one side, and 

 slightly bent backward, so as to form jutting processes, which 

 meeting grew together, became confluent, and developed into a 

 sporangium much larger than either of the parent cells. Into this 

 sporangium the contents of the latter passed, and soon became 

 converted into a thick-walled spore, often completely filling the 

 cavity, and apparently with its wall adherent to that of the latter. 



BRITISH GEASTERS. 



In the columns of the " Gardener's Chronicle, 1 ' Mr. Worthington 

 G. Smith has from time to time contributed a synopsis of the 

 British species of Geaster, with illustrations, which, by the kind 

 permission of the editor and proprietors of that journal, we have 

 been permitted to reproduce for the benefit of our readers. 



1 Geaster coliformis. P.— Cooke's " Handbook," No. 1070. 

 « Gardener's Chronicle," 1873, p. 469, fig. 86. [PI. xv., fig. 1.] 



Spores -0002 in. diam. 



