﻿1 903 ] CURRENT LITER A TURE 1 4 5 



exact methods in the study of the growing point, and takes great pains to 

 secure exactly median and very thin sections. 



In the second part he describes his examination of the stems of a large 

 number of dicotyledons and monocotyledons, for the presence of an endoder- 

 mis (phloeoterma of Strasburger), and from his own observations and the litera- 

 ture of the subject draws up a comprehensive tabular view of the occurrence 

 of this layer. He finds, contrary to Fischer, that an endodermis is a very 

 constant feature of the stem in monocotyledons, being present in 18 families 

 out of ig investigated. In the case of the dicotyledons, it was present in 99 out 

 of 169 families. The author draws the conclusion that the endodermis is a 

 very important layer morphologically. Taking Into consideration the recent 

 work on the ontogeny of the central cylinder, he agrees with Boodle, that the 

 central cylinder of all vascular plants is morphologically the same, viz., 

 monostelic. — E. C. Jeffrey. 



Willis, ^9 in continuing his studies of the oriental Podostemaceae, has 

 published a most interesting account of the habits and ecological relations of 

 the Ceylonese and Indian forms. All members of the family live in rapidly 

 moving water, usually in the rapids and waterfalls of mountain streams. In 

 general they are attached to rocks, each species affecting a particular habitat, 

 determined by speed, depth, and roughness of the water. These various 

 factors are fully described under each species. The most problematical and 

 characteristic structure of the group is the so-called " thallus," a creeping 

 dorsiventral organ developed from the primary axis, and itself bearing 

 endogenous secondary shoots. In different genera the thallus seems to be of 

 different morphological value, but in the main it has been regarded as a root 

 structure, which raises a question as to the essential character of a root. In 

 any event, the function of the thallus, which often resembles an alga, a lichen, 

 or a liverwort, is to spread rapidly over rocks, developing new shoots at short 

 intervals, and holding them in the swiftly running water until they can form 

 holdfasts of their own. 



Probably the most significant part of the paper is the discussion of the 

 dorsiventrality of the group, no other family above liverworts showing so 

 marked and far-reaching a dorsiventrality in organization. The author pre- 

 sents a series of forms passing from the least modified forms, in which dorsi- 

 ventrality is only expressed by the position of the thallus, to the most highly 

 modified forms, in which dorsiventrality appears in every part, even in the 

 embryo. The very interesting conclusion is reached that, as inthewhole family 

 dorsiventrality appears first in the vegetative organs and then includes other 

 members, the dorsiventrality of the flowers, which is the most important 

 diagnostic feature of the family, is a direct result of that of the vegetative 

 organs; in other words, that the dorsiventrality of the floral organs has been 



^nViLLis, J. C, Studies in the morphology and ecology of the Podostemaceae of 

 Ceylon and India. Ann. Roy. Bot.. Gardens Peradeniya i : 267-465. ph, 4-3^^ 1902. 



