56 PROCEEDINGS OP THE AMERICAN ACADEMY. 



If a small portion of the upper part of a branch be gently crushed 

 between a slide and a cover-glass, one can readily see all the principal 

 stages in the growth from the apical cell, even to the production of 

 the complexity of tlie adult frond. By a judicious agitation of the 

 cover-glass by tapping gently, the various sets of cells may be made 

 to separate in such a fashion as to show all the lesser details. The 

 old frond is so dense as to be crushed with some difficulty, and in the 

 process the relations are often more or less obscured. Therefore 

 sections are a necessary aid to understanding the structure of such 

 portions, but can be made in any direction with considerable ease. 

 During the investigation of the development of the frond, the sexual 

 organs and developing fruit were discovered and carefully studied. 

 By this, we are enabled to make our comparison more thorough and 

 more exact. 



Tuomeya jlaviatilis is found in brooks or small streams, and seems 

 to prefer those windings of the course or declivities in the bed where 

 the current is accelerated. It grows for the most part on smooth 

 stones or rocks, clustered together in considerable numbers. In a 

 few cases, Mr. Holden has found it growing upon grasses. When 

 kejit in the house, Tuomeya generally flourishes well, if the tempera- 

 ture be not too high, and if it has an occasional supply of fresh water. 

 It often puts forth new branches under such circumstances, and one lot 

 even produced the sexual organs. 



In regard to the general habit of the plant, Harvey's description 

 can hardly be improved upon. It scarcely ever reaches a height of 

 over two inches (5 cm.), is pyramidal or irregularly conical in general 

 outline, and decidedly bushy (cf. Fig. 1). The plant is comparatively 

 rigid, and does not collapse on being removed from the water. In 

 this respect, it differs much from the larger specimens of Batraeho- 

 spermum, which it greatly resembles in size, color, and manner of 

 growth, and with which it very frequently grows. Indeed, it is often 

 difficult to tell Tuomeya, when gi-owing, from one of these larger 

 JBatrachosperma, unless one touches the specimen or takes it from the 

 water. The Tuomeya then remains firm and retains its shape, while 

 the Batrachospermum titterly collapses and becomes a shapeless gelati- 

 nous mass. The younger branches of Tuomeya, however, are often 

 very slender, and then generally droop considerably on being with- 

 drawn from the water, but to no such extent as is characteristic of 

 the Batrachosperma. "When dried, specimens of Tuomeya seem to 

 be decidedly cartilaginous, resembling in this respect specimens of 

 Ahnfeldtia plicata. They do not adhere closely to paper, even after 



