4S SUMMARY OF GUItLtKNT KKSKARCHES RELATING TO 



atmospheres. When the seed-coai is removed from the large end of the 

 embryo, the latter is free to swell, and the seed gains LOO p.c. in weight 

 in 20 hours. II' the coal is removed from both ends, the embryo 

 elongates L9 p.c. in 2\ hours ami 30 p.c. in ."> hours. This elongation is 

 only due to growth in a very small degree, but an increase of 36 p.c. in 

 length after 16 hours soakiug involves considerable growth. Tin- seed- 

 coat is composed almost entirely of pectic compounds, easily transformed 

 by weak acids and bases. A.cids appear to increase the absorptive powers 

 of the embryo and bases increase the rale of elongation, so that both 

 bring about a weakening of the seed-coat. In common with the seeds 

 of many other aquatic plants, the seeds of Alisma are capable of retain- 

 ing their vitality for many years, when saturated with water. The 

 embryo can elongate 120 p.c. at the expense of its stored foods, in the 

 absence of free oxygen, but the latter is necessary for the development of 

 the radicle and plumule and for the formation of chlorophyll. 



•CRYPTOGAMS. 



Pteridophyta. 



(By A. Gepp, M.A., F.L.S.) 



Spermatogenesis in Marsilia.* — L. W. Sharp gives an account of 

 spermatogenesis in Marsilia. In 11)12 f he showed that the blepharo- 

 plasts of Bryophytes, Pteridophytes, and Gymnosperms are derived onto- 

 genetically or phylogeneticafly from centrosomes. He summarizes his 

 j tresent paper as follows : — 1. In the first spermatogenous mitosis there 

 is present at each spindle pole a dense region with radiations, but no 

 centrosome. 2. During anaphase of the second mitosis a centrosome 

 develops at each spindle pole, and at telophase divides to two daughter- 

 centrosomes. These only rarely develop farther ; they usually de- 

 generate at once in the cytoplasm. 3. In the third mitosis a centrosome 

 develops at each spindle pole at anaphase exactly as in the second 

 mitosis, and during telophase or later divides to two daughter-centro- 

 somes. 4. These daughter-centrosomes, which may now be called 

 blepharoplasts, move apart and occupy the spindle poles through the 

 fourth or final mitosis. 5. The centrosomes are at all times accompanied 

 by extensive radiations, which in the fourth mitosis give rise to the 

 achromatic figure. When the centrosome divides there is present a 

 central spindle and amphiaster as in animal cells. (!. Before the fourth 

 mitosis is completed the blepharoplast becomes vacuolate and breaks up 

 into a number of fragments. In the spermatid these form a band which 

 elongates spirally in close union with the nucleus and bears the cilia. 

 7. The evidence afforded by Marsilia, together with that gained from 

 other plants and certain animals, is believed to show conclusively that 

 the blepharoplasts of Bryophytes, Pteridophytes, and Gymnosperms are 

 derived ontogenctically or phylogenetically from centrosomes. 



* Bot. Gaz., lviii. (1914) pp. 419-31 (2 pis.). 

 t Bot. Gaz., liv. (1912) pp. 89-119. 



