ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 589 



tative cells contain G4 chromosomes, but this number is reduced to 32 

 in the four nuclei resulting from the first two divisions of the oogonium 

 and antheridium. These 32 univalent chromosomes persist up to the 

 formation of the sperm and egg, and the whole of this phase may be 

 regarded as the gametophyte generation. The union of gametes again 

 brings the number up to 64, and this condition, which persists until the 

 formation of the first four nuclei in the oogonium and antheridium, is to 

 be regarded as the sporophyte generation. Thus Fucus exhibits a well- 

 marked alternation of generations. 



Spermatogenesis in Dioon.* — 0. J. Chamberlain has examined the 

 staminate cone of Dioon edule, and finds that the sporophylls are large 

 and bear about 250 sporangia. Each sporangium yields about 30,000 

 spores. The pollen-mother-cell has twelve chromosomes, but owing to 

 early splitting the number appears larger. The single prothallial cell 

 is persistent. The blepharoplasts arise from the nucleus with radiating 

 streams of cytoplasm ; the solid blepharoplast breaks up into granules, 

 from which a spiral band is formed. The sperms are formed within the 

 sperm-cells, and are larger than those of Cycas or Microcycas, but smaller 

 than those of Zamia. Both nucleus and cytoplasm show a strong 

 amoeboid movement in addition to the ciliary movement. Later on the 

 author intends to discuss the question of phylogeny. 



Structure and Development. 

 Vegetative. 



Vascular Anatomy of Microcycas. t—H. A. Dorety has studied the 

 vascular anatomy of the seedling of Microcycas ccdocoma. The following 

 are the chief results of her investigation. There are two hypogeal 

 cotyledons which often fuse, and the plumule escapes by burstingthe 

 cotyledonary sheath. Root-formation is delayed. Mucilage ducts 

 alternate with the cotyledonary strands. The siphonostelic hypocotyl 

 has no cortical vascular tissue, but there are traces of a broken cambial 

 zone. The strands of the cotyledons are endarch below and exarch 

 above ; those of the petiole are all exarch. The root is tetrarch, but 

 may be triarch at the tip. 



Progress of Plant Anatomy.}— E. C. Jeffrey contributes a paper 

 upon the progress of plant anatomy during the past decade. The author 

 draws attention to the importance of the study of the gametophyte 

 generation, and especially of the male gametophyte. The evidence 

 derived from this source, however, is much extended by the study which 

 has recently been devoted to the sporophytic generation of' higher 

 plants, where anatomical characters are as important as cytological 

 phenomena. In proof of the value of anatomical investigations, a few 

 examples are cited, notably that of the phylogenetic position of Pinus, 

 which is now shown to be of much greater antiquity than the Yews. 



* Bot. Gaz., xlvii. (1909) pp. 215-36 (4 pis. and 3 figs.). 



t Tom. cit. pp. 137-47 (2 pis.). % Amer. Nat., xliii. (1909) pp. 230-7. 



