54 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



Liverwort Types for Elementary Classes.*— W. C. Coker raises a 

 protest against the use of so complex and difficult a plant as Marckantia 

 for demonstrating- to students the structures concerned in the alterna- 

 tion of generations. The complex thallus, the stalked and still more 

 complex archegoniophores and antheridiophores, the hidden antheridia, 

 the small sporophytes concealed amid delicate vestments difficult to 

 distinguish, render Marckantia a formidable object to the beginner. 

 Far better and simpler is such a type as Pallavkinia Lijellii, in which 

 by one section may be shown a longitudinal view of the young sporo- 

 phyte and its envelopes, and a transverse view of the gametophyte. 

 The male plant is equally simple, and the antheridia large. For showing 

 the structure of the capsule and the relation of its contents, he prefers 

 a species of Frullania. Here the elaters extend the whole length of the 

 capsule and alternate with single rows of spore mother-cells. 



Physiology of Liverwort-rhizoids.f— H. "Weinert has investigated 

 the growth and the phenomena of tropistic movements of the rhizoids 

 of thalloid liverworts under the influence of light and gravity, also the 

 physiology of the tuberculate rhizoids. He finds that bright light is 

 favourable to the development of the rhizoids. In the dark no 

 spreading rhizoids are formed, and fewer than usual of the appressed 

 tuberculate rhizoids. Blue and red lights suppress the formation of 

 rhizoids. Injured rhizoids do not undergo regeneration. As regards 

 the gemma?, their production of rhizoids is extraordinarily sensitive to 

 the access of water, and the outgrowth of rhizoids on the under side is 

 induced by gravity ; they are also negatively heliotropic. The thallus 

 rhizoids are little or not at all affected by unilateral illumination. Red 

 rays have a strongly negatively heliotropic effect upon the gemmaj- 

 rhizoids. Blue light has no heliotropic effect on the rhizoids. Gravity 

 has no effect upon the rhizoids of thallus or gemmae, either at the time 

 of growth or afterwards. The appressed tuberculate rhizoids are not 

 tropistically affected by either lateral illumination or gravity. 



Biology of the Archegonium and Calyptra. J— F. Zielinski dis- 

 cusses the biology of the archegonium and of the calyptra of mosses. 

 In summing up his results he says :'— 1. The opening of the archegonium 

 is due to separation of the apical cells, brought about by the slime 

 imbedded in the cells. 2. The calyptra separates itself from the 

 vaginula along a zone specially prepared for the purpose. Many mosses 

 have an inflated calyptra which serves as a water-store, from which 

 the embryo in early stages can absorb water. 3. The greater or 

 lesser development of the calyptra is proportional to the greater 

 or lesser susceptibility of the sporogonium to external injury, especially 

 to drought. Sporogonia which have been robbed of their calyptra 

 accelerate their growth and strive to attain maturity. 4. The formation 

 of hairs on the calyptra is the clearest expression of the above-mentioned 

 susceptibility, and bears a direct relationship to the habitat of the 

 respective mosses. It is sometimes liable to become obscured by other 



* Torreya, ix. (1909) pp. 233-6 (figs.). 



t Bot. Zeit., lxvii. (1909) pp. 201-31 (figs.). 



X Flora, c. (1909) pp. 1-36 (figs.). 



