-492 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Ascophyllum-galls caused by Mytilus edulis.*— F. Tobler has 

 studied specimens of Ascophyllum nodosum which had air-vesicles in- 

 fested with larvse of Mytilus edulis, which form their shells inside and 

 split the vesicles. The broken vesicles exhibit on the inner wall a 

 heteroplastic formation — a kind of cortex, which arises below the 

 normal hair-cells of the wall, being caused by irritation and favoured by 

 illumination. Such formations do riot occur in the tissues where 

 normal growth has ceased. The occurrence of such formations in the 

 inner tissue tends to check further development of the cortex. The 

 growth of the animal's shell stretches aud rends the tissue, and gives a 

 clue to the direction and force of the strain. The breaking away of 

 parts of the frond sets up a demand for a strengthening of the 

 mechanical tissues, and this is provided for by a development of the 

 medullary hyphse. 



Juvenile Kelps and the Recapitulation Theory.f— R. F. Griggs 

 writes very fully on this subject, and divides his paper into two sections : 

 1. The development of certain kelps. 2. The recapitulation theory in 

 relation to the kelps. In the first section the author describes in detail 

 and gives figures of the early stages of Rmfrewia, Lessoniopsis, Egregia, 

 and HedopltyJhmi. Of all the kelps Egregia is the most specialised, and 

 represents the highest type. In the second section the author discusses 

 the opinions of Montgomery, His, and Morgan on the recapitulation 

 theory, and then considers the development of the kelps in relation to 

 the theory and to their criticism upon it. Finally the author comes to 

 the conclusion that, taking all the evidence into consideration, we are 

 bound to conclude that, though organisms are subject to adaptation at 

 any stage of their life-cycles and may gradually cut out superfluous 

 stages, yet, except as some such tendency has operated to change the 

 heritage, the development of the individual does recapitulate the history 

 of the race. 



Sporophylls of Lessoniopsis.:]:— R. F. Griggs describes the develop- 

 ment of the sporophylls of Lessoniopsis litoralis. In the sterile frond 

 the laminae are increased in number by repeated median longitudinal 

 splitting, which begins at the base as a perforation and extends up the 

 midrib to the apex. Each half becomes symmetrical by growing a 

 second wing or ala. The sporophylls, on the other hand, possess no 

 midrib, and their origin is different. They arise as lateral outgrowths 

 from the meristem below the base of the lamina, thus corresponding 

 with the sporophylls of Alaria and Pterygophora. As in the latter, they 

 are at first cylindric at the base ; but as they grow they flatten into a 

 sessile spatulate blade usually falcate, widest at apex and cuneate at 

 base, and 3 inches long. They slowly increase to the length of the 

 sterile lamina? and become semicircular or subcordate at base. The 

 diverse character of the laminae led Reinke to remove the plant from 

 Lessonia and create for it the genus Lessoniopsis. Phylogenetically it 

 is of interest as showing affinity to both of the principal lines of de- 



* Pringsheim's Jahrb. wiss. Bot., xlvi. (1909) pp. 568-86 (1 pi. and 2 figs.), 

 t Arner. Naturalist, xliii. (1909) pp. 5-30, 92-106 (figs.). 

 % Ohio Naturalist, ix. (1909) pp. 437-9 (figs.). 



