ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 149 



of the zoospore. At other times it elongates into a filament, generally 

 short, the cells of which afterwards grow irregularly, remain simple or 

 divide transversely or longitudinally. All the cells of the female 

 prothallus have the same value and each may be transformed into an 

 oogonium, the order of transformation being independent of the 

 respective age. It then produces an erect protuberance, perhaps two ; 

 sometimes the protuberance is very long, and in that case it often 

 divides slowly in a transverse direction. The protuberance becomes the 

 neck of the oogonium, aljout 9 /x broad. When an oogonium approaches 

 maturity the chromatophores multiply at the distal end, which becomes 

 tightly packed with them. Then' the wall increases by swelling all 

 along its inner surface, and particularly at its distal extremity. Finally, 

 the compressed contents escape and remain above the oogonium, where 

 they take a long oval form. The inconstancy of the dimensions of the 

 oogonium cause a variation in the volume of the oosphere, which is in 

 any case a very large body compared with the antherozoids. l^ehisceuce 

 is effected by a median rupture of the swollen extremity, the edges of 

 which at once rejoin and form a sort of thick staging on which the 

 plantlet is to rest. If the base of the oosphere is attenuated and does 

 not manage to emerge, the swollen edges which are prevented from 

 rejoining hold it up on the bottle-neck, as in Saccorhiza. In the former 

 case the first rhizoid will be exterior to the oogonium ; in the latter it 

 will descend into the cavity. An oogonium which has put out two 

 protuberances, only dehisces by one of them, the other remaining a 

 €ul-de-sac. A cell underlying an empty oogonium elongates sometimes 

 into the cavity and dehisces, while pushing aside the first plantlet. As 

 in Saccorhiza the egg germinates without undergoing a resting period. 



Growth in LaminariacesB.* — Annie L. Fallis records the result of 

 her experiments on the growth of Lcmunaria, Agaruni, Gymatlisere, 

 Eijregia, Alaria, and Nenocystis. She found that the plants grow as 

 •well suspended from a raft by means of cloth strings as they do when 

 attached naturally to the rocks by their own holdfasts. She found also 

 that the removal of the holdfast, and even of a considerable portion of 

 the stipes, does not affect the growth of the remainder of the plant. 

 The removal of the tip of the blade produces only a negligible effect so 

 long as the basal portion is left intact. Pieces of the lamina, even as 

 small as 1 mm. square, were found to grow when placed in a cloth bag 

 attached to a raft. In kelps having a very short stipes it was found 

 that the region of the greatest growth in the post-juvenile stages is near 

 the base of the lamina, the main growth of the stipes occurring during 

 the younger stages. The kelps experimented upon grow almost twice 

 as rapidly during the daytime as during the night. The results reported 

 agree well with the small degree of physiological specialization of parts 

 that is found in such genera as Laminaria and other leaf-like kelps. 



* Puget Sound Marine Stat., Publ. i. (1916) pp. 137-55 (4 pis.). See also Bot. 

 Oaz., Isii. (1916) pp. 332-3. 



