242 BOOKS AND CURRENT LITERATURE 



Sexual organs are distributed over the entire surface as a rule, al- 

 though in a few cases, one surface was quite fiee from both sexual or- 

 gans and rhizoids, thus suggesting dorsiventrality. Both antheridia 

 and archegonia are found in large numbers intermingled on the same 

 gametophyte, arising in acropetal succession from the apex. The 

 antheridia fonn hemispherical protuberances when mature; the arche- 

 gonia have straight projecting necks which later are cut off so that the 

 appearance is much altered, — a condition that has been misinterpreted 

 by Lawson.^ Mature antheridia present an appearance similar to the 

 marginal antheridia of Equisetum in their projecting nature; they pos- 

 sess a quadrangular opercular cell which disintegrates, allowing the 

 escape of the speims. The projectmg portion of the antheridial wall 

 originates from the primary wall cell and is one cell thick; the basal 

 part of the wall comes from the cells bordering the spermatogenous tis- 

 sue which develops from the inner or primary spermatogenous cell. 

 Unfortunately neither sequence of cell divisions nor spermatogenesis 

 was worked out, nor does either description or figure reveal the type of 

 sperm. In archegonial development the primary neck cell produces a 

 neck of three or four tiers of four cells each, which eventually is cut off. 

 The author states, that he failed to determine the sequence of divisions 

 here also, but that a basal cell is not formed. 



Fertilization is not taken up. After enlarging considerably, the fer- 

 tilized egg divides equatorial] y into epibasal and hypobasal cells, and 

 the hypobasal half again divides by a vertical wall. From here on the 

 sequence is uncertain so far as the paper is concerned. An apical cell 

 is formed from tissue developed by the epibasal cell according to the 

 writer's interpretation, thus suggesting Equisetum and Ophioglos- 

 sum, and disagreeing with Lycopodimn, while the hypobasal cell gives 

 rise to the foot. The latter consists of numerous, finger-like haustoria 

 which penetrate the gametophytic tissue and are in close relation above 

 with the main vascular strand of the sporophyte. Just above the foot 

 is a meristematic zone which the writer is unable to interpret. No coty- 

 ledon appears, the first leaves coming in late in the form of scales, from 

 segment of the apical cell. The young rhizome is a monarch protostele 

 which passes into a siphonostele with several xylem groups, in the older 

 rhizomes — a condition "in no wise occasioned by any branching of the 

 stele." The mesarch condition is the highest level reached. No sec- 



- Lawson, A. A., The prothallus of Tmesipteris tannensis. Trans. Royal 

 Soc. Edin. 51, pt. iii: 785-794, 1917. 



