252 



THE JOURNAL OF BOTANY 



which it is hoped will soon appear, must gain largely in interest by 

 a study of this examination of Dktijosiphon by Dr. Murbeck. 



The section describing the strain arising from unequal growth 

 of the innermost and outermost cells of the thallus is perhaps the 

 most interesting, as touching on wider biological questions than 

 can be raised in the other parts of the paper. As the author says, 

 the question of the tension of tissues in marine algae is a subject of 

 recent study only, and the result shows a marked contrast to the 

 mode of tension in the higher plants. This is of course to be 

 expected in view of the wholly different surroundings of the two 

 groups. Among the algae, except in the case of those which secrete 

 lime, everything makes for greater flexibility and elasticity, and, 

 even among plants and animals hardened by an outward secretion 

 of lime, there remains, as is shown by Prof. Stewart in his paper 

 on the subject,'^ uncalcified nodes between each joint, which prevent 

 the plant from becoming so rigid as to cause its destruction from 

 the movement of the water. It is obvious that in fairly large plants, 

 such as Dictyosiphon fmiiculaceus, some such elasticity as is described 

 by Dr. Murbeck is necessary for their protection. 



The growth of the hairs is fully described and figured, but no 

 new facts are given concerning the use to the plant of these growths, 

 so common among the PhcEophi/cecB. The formation of pits, the 

 consequent enlargement of the surface of the thallus, and Prof. 

 Reinke's theory as to the possible employment of the hairs in 

 abstracting mineral substances from the water, is brought forward, 

 and the experience of the author, in common with others, is shown 

 to be that the more plentiful the hairs, the finer the plant. But 

 which is cause and which effect ? When will someone experiment 

 on this point in the growing plant ? 



The occurrence of hyphae in D. fceniculaceus is here demonstrated 

 for the first time, though they were already known in Z). hippuroides, 

 The interest lies, however, less in this fact than in the irregularity 

 of their occurrence in the thallus, being found in large quantities 

 in some parts, and in others not at all. The Wille theory as to the 

 connection of hyphae with the assimilation of COg seems hardly to 

 fit a case like this, and there are also difficulties in the way of re- 

 garding them as mechanical supports. A study of allied Phceophycea 

 is necessary for a solution of this question. 



A description of the mode of attachment between D. fceniculaceus 

 and Chordaria, on which it grows, shows an ingenious intermingling 

 of the two plants at the point of junction, and it would be interesting 

 to study the mode of attachment of other members of the family, or 

 of this one on other hosts. 



* Cat. Comp. Anat. R. Coll. Surgeons, i. 54. 



