Tilden: MORPHOLOGY OF hepatic elaters. 51 



cells in the air passages of the stalks of many water plants, e. g. 

 Eriophorum and Scirpus lacustris and of stellate hairs in the petiole 

 of Nuphar, (3) the occurrence of thyloses in the tracheas of many 

 Dicotyledonous woody plants {Quercus, Samhucus, Cucurbita, etc.) 

 and some Monocotyledons (Canna, Palms, etc.). In connection 

 with this matter an interesting paragraph is found in Goebel's 

 Outlines^''' where he observes: "In parenchyma of the funda- 

 mental tissue of the leaves [Marattia, Angloj^teris, Danaea, and 

 Kaulfussia), Liirssen^^ found outgrowths on the walls of the 

 cells bounding the intercellular spaces; these outgrowths pro- 

 ject into the spaces, and where these are small, they take the 

 form of bosses or conical projections, but in larger ones they 

 become long, slender filaments, which are quile solid and con- 

 sist of cuticularized substance; large intercellular spaces are 

 quite filled with a web of these filaments." In this case the cell 

 wall alone undertakes the space-filling function. 



As to the point at which the bud appears, this may depend 

 upon several things: (1) There may be slight differences in the 

 thickness of the wall of the elater, and if so, the protuberance 

 will occur at a thinner rather than at a thicker part, for that 

 will have the greater extensibility. (2) There may be variable 

 areas of maximum turgescence in an unsymmetrical cell, and as 

 a matter of course, a bulging or swelling out would be caused 

 where there was the greatest pressure. ( 3) Again, it is readily 

 conceived that there may be and probably is some relation be- 

 tween the branching of the elater cell and the distribution of 

 bands; but this relation is not easily defined. Whether the 

 spiral band is principally concerned in the process and by its 

 more vigorous growth stretches out the cell membrane, or 

 whether the impulse is given to the membrane itself, and the 

 band merely keeps pace with it in growth, or is formed some- 

 what more tardily, is a matter which will require much more 

 study before a conclusion can be reached. In general, the bud, 

 from its earliest appearance, is seen to be encircled by one or 

 more loops {PL IV. fig. 8, b; fig. 13, a; PL V. fig. 12, a. b.). but 

 exceptions to this rule occur {PL IV. fig. 6, c; PL V. fig. 4. d.). 

 (4) Perhaps, also, the varying thickness or width of the bands 

 may exert some influence. 



The branching of the elater itself necessarily leads to pecul- 

 iarities and complexities in the branching of the spiral bands. 

 In one case {PL V. fig. 1 ) the spiral band branches (a) shortly 



45. Goebel, Outlines. 255. 1887. 



46. Liirssen, Hiindb. d. Syst. Bot. 1 : ,577. 1879. 



