78 C. M. CHILD. 



simultaneous throughout the length, and where the gradient is 

 acropetal it begins at the basal end of the protoplasm and pro- 

 ceeds acropetally. The deep stain of the masses scattered along 

 the cell rapidly fades and the hair presents almost the appearance 

 of the normal hair, but a careful examination with proper illu- 

 mination shows the aggregated protoplasmic masses which are 

 still transparent and are visible only because of their refractive 

 index. 



The hairs of Chondrus crispus and Agardhiella tenera are 

 similar in structure to those of Ceramium and the few incidental 

 observations made on these species indicate that they behave in 

 essentially the same way. The hairs on freshly collected plants 

 in good condition usually show a basipetal gradient. Most of 

 the hairs die during the first two or three days in the laboratory 

 and acropetal gradients with decreased susceptibility are often 

 observed before they die. Plasmolytic separation or basal re- 

 traction of the protoplasm also often precedes death and the 

 final changes are similar to those in Ceramium.. In the hairs of 

 Ceramium and Agardhiella the basal retraction of protoplasm 

 often occurs merely as the result of laboratory conditions and 

 before death the entire protoplasm of the hairs may be contracted 

 into a mass one fifth or less of the length of the hair, lying near 

 the apical end and as might be expected, staining much more 

 deeply than in the normal condition. Similar changes probably 

 occur in the hairs of Chondrus but have not as yet been looked for. 



UNB RANCHED MULTICELLULAR HAIRS. 



Hairs of this kind consist of a single series of cells (Figs. 2 and 3) , 

 and in the only two species examined, Fucus vesiculosus and 

 Castagnea tuberculosa, the vegetative point of the hair is at its 

 attached basal instead of at the free apical end. Because of 

 this fact observations on the susceptibility gradients of these 

 hairs are of particular interest. 



In Fucus the hairs develop from the inner walls of flask-shaped 

 cavities on the thallus, and later from the walls of the concep- 

 tacles. The hairs reach the exterior through the narrow neck of 

 the cavity and form dense tufts, often several millimeters long. 

 As noted above, the growing point of the hair is basal, i. e., next 



