292 



MacMillax: Observations on Nereocystis 



^ 4 



and lamina which are with some hesitation termed cryptostomata 

 appear as short, irregular furrows from the surface of which tufts 

 of two- or three-celled hairs are produced. They are not so con- 



V 



spicuous in Nereocystis material that I have examined as those of 

 Adcnocystis, A/aria and SaccorJiiza described by KjeHman and 

 IMurray. I have failed to find them save on young plants less than 

 half a meter in height. Various suggestions have been made by 

 different students of the Phaeophyceae regarding their significance. 

 By some they are regarded as vestigial reproductive tracts, but it 

 will be unnecessary to go into this further than to make the sug- 

 gestion that the areas classed as cryptostomata in different genera 

 of brown algae are not by any means necessarily to be considered 

 as everywhere the same. Indeed it is quite clear that in the 

 Splachnidiaccae and Laminariaceae they are probably of different 

 significance from those of Fucaceae. They stain deeply with 

 aniline dyes in Kercocystis and I suspect from this fact that I have 

 not seen mature stages of the hairs. There is a possibility that the 

 mucilage canals are invaginated furrows and that the so-called 

 cr}'ptostomata are developmental stages of these, but I ha\-e not 

 satisfied myself upon this point. 



Primitive Furrmvs of the Lamina, — 



— An interesting character 



'which is to be noted in very young plants is a longitudinal furrowing 



of the lamina by parallel grooves which occur on both sides, each 



groove lying over a mucilage canal. In the primitive tip where mu- 



cilagfe canals are absent the furrow^s also are absent and leaves tw^o or 



I 



three centimeters in length have lost these furrows as may be seen 

 in cross section, but in plants i-2 cm. in height a deep furrow lies 

 over each longitudinal mucilage canal just within the epidermis. 

 Something of an appearance similar to that of young Costaria 

 plants is given by these longitudinal furrows. But in Costaria the 

 striation of the lamina arises, as shown by cross sections, from 

 ridges which structurally belong to the cortex and o\'cr which the 

 epidermis is elevated by the growth of inner portions of the lamina. 

 Nor in Costaria do the ridges bear the same relation to mucilage 

 ducts that is borne by the primitive furrows in the Nereocystis 

 sporeling. Indeed I have not observed mucilage ducts in young 



Costaria laminae. 



Origin of Secretion-cells in the Lamina, — It has already been 



