282 NOTES ON SARCOMENIA MINIATA AG. 



pericentral tube. The stem is of a narrow elliptic form, since, 

 seen on a cross-section, there are three cells lying one behind the 

 other in one direction, and five cells in the other. The pericentral 

 cells have not the same morphological value, for a cross-section 

 shows clearly that the diameter of the lateral tubes from front to 

 back is nearly as broad as the diameter of the three middle cells 

 taken together (fig. 2). 



Fig. 1 is a diagrammatic drawing of the top of a branch, and 

 shows the way in which the tubes and cortical cells are developed. 

 This process is exactly the same as that described by Prof. Cramer"" 

 for the first divisions of the genus Calxjlossa ; the structure of 

 CaIo(/lossa, however, being more complicated than that of Sarco- 

 meniti, the subsequent changes that take place in the segments are 

 different. The initial cell of Sarcamenia divides first by a horizontal 

 wall ; the segment thus cut off shows first one and then a second 

 vertical partition, dividing the segment in three equal portions. 

 The exact moment when the tangential walls appear, that cut out 

 the front and back pericentral tube, could not be ascertained, but all 

 these divisions take place very quickly one after another. The 

 lateral tubes are afterwards partitioned by two oblique walls 

 extending from the middle of the upper or the lower wall to the 

 middle of the outer wall, and the segments thus cut off form the 

 row of cortical cells. I was anxious to know whether some of 

 the adaptations in Calor/lossa to prevent the decay of the stichidia 

 after the departure of the tetraspores were to be found also 

 in Sarcomenia; my supposition was confirmed for the branches 

 destined to become stichidia ; the lateral tubes, after having given 

 off' the cortical cells, divide again by a vertical wall into two equal 

 cells. The back one — by whicli name for clearness' sake I dis- 

 tinguish the cell that will bear no tetraspores — undergoes no further 

 ciianges. The front one is cut in two by a horizontal wall ; the 

 upper cell resulting from this partition becomes the mother-cell of the 

 tetraspores ; the lower one is a kind of stalk-cell to the sporangium, 

 and may also serve to consolidate the stichidia (figs. 3, 4, 5). 



During this process each cortical cell divides again by an 

 arcuate wall into a small upper and a bigger lower cell, this last 

 one bearing some resemblance to a crescent with rounded horns. 

 After the maturity and escape of the tetraspores, these horns push 

 forth to the empty sporangia from where the tetraspores have fallen 

 out by a slit in the membrane, and dividing themselves give rise 

 to cortical cells that take the place of the sporangia. This has a 

 double advantage for the plant : first, the vegetative life of the 

 stichidia will be lengthened, for these new cortical cells will protect 

 the stichidia from being torn off by the current, which might easily 

 happen after the tetraspores have left the sporangia ; and secondly, 

 it must not be forgotten that the branches of Saicomcnid miniata 

 have all an acropetal growth. The tetraspores at the base of the 

 stichidia are long ripe, have in fact often left the sporangia, before 

 Two of these cortical cells have the same length as one cell of the 



* Cramer, C, Ueber Caloglossa Leprieurii Harv., J. G. Ag. Tab. ii. figs. 1 & 2. 



