66 SUMMARY OF CURRENT RESEARCHES RELATING TO 



nucellus varies considerably and may exhibit all degrees of reduction ; 

 the archesporium, however, is more uniform, and consists of four cells^ 

 the lowest of which forms the embryo-sac. In the Asclepiadacese, the 

 bicarpellary ovary has numerous ovules which exhibit remarkable 

 uniformity of structure and development. The twelve genera studied 

 all exhibit the same characters as has been observed in Apocynum. The 

 nucellus is represented by the archesporium and rudimentary epidermis, 

 but the latter disappears during the development of the tegument. 

 Such peculiarities as are found in this group leave no reason to suppose 

 that it does not follow the normal course of development in the 

 Gamopetalffi. The reduction of the nucellus must be regarded as a 

 condensation of development adapted to the rapid formation of the 

 tegument of the ovule. This is a constant and interesting character of 

 the Asclepiadacea?, marking a very liigh degree of differentiation. The 

 author will publish shortly a complete account of the investigations, 

 reviewed in this preliminary paper. 



CRYPTOGAMS. 



Pteridophyta. 



(By A. Gepp, M.A. F.L.S.) 



Stelar system of the Marattiacese.* — C. West, in giving the results 

 of a comparative study of the structure and development of the stelar 

 system in the Marattiaceje, with special reference to the adult sporophyte 

 of Dansea, discusses the quescion of the symmetry of the sporophyte in 

 the Marattiacefe. He states that : 1. A primitive radially symmetrical 

 type of shoot is distinctly suggested. 2. The single apical cell of the 

 stem of the young sporeling is later replaced by a group of equivalent 

 initial cells or by a meristematic region. 3. A single large apical cell 

 occurs at the apex of the primary and earliest adventitious roots. At 

 the apex of the later adventitious roots of moderate size a group of 

 about four equivalent initial cells is found, while the more robust roots 

 generally possess a definite meristem consisting of a numbei' of indepen- 

 dent initial cells. In brief, the number of initial cells found at the 

 apex of the Marattiacean roots is clearly related to the bulk, and not 

 necessarily to the age of these roots. 4. The six genera which com- 

 prise the Marattiaceffi show remarkable uniformity in their morpho- 

 logical, anatomical, and histological characters, and constitute a very 

 homogeneous and natural family, which probably occupies an isolated 

 position amongst modern Vascular Cryptogams. 



Equisetum dehile.t— S. R. Kashyap publishes some notes on the 

 endodermis and the prothallium of Equisetum dehile Roxb, 1. The 

 endodermis in this species is very unstable. At the nodes it surrounds 

 each vascular bundle of the underground and of the aerial sterile shoot ; 

 but in the internodes of these shoots there is a transition from this con- 



* Ann. Bot., xxxi. (1917) pp. 331-414 (2 pis. and figs.). 

 t Ann. Bot., xxxi. (1917) pp. 4-39-45 (figs.). 



