ZOOLOGY AND BOTANY, ^MICROSCOPY, ETC. 687 



number being 7. There is doubt as to the origin of the heterochromo- 

 somes, which are present in all the reduction divisions, and until this 

 point is settled, no significance can be attached to them. In the telo- 

 phase of the heterotypic mitosis in the pollen-mother-cells of the 

 Lamarckiana hybrid, the chromosomes are in tetrads. In the homotypic 

 mitosis of 0. Lamarckiana, and in the somatic mitoses, the chromosomes 

 are two-iobed in the telophase. The tetrad appearance in the first case 

 is probably due to the same lobing of the bivalent chromosomes of the 

 latter case. 



Structure and Development. 

 Vegetative. 



Development of Pinnate Leaves.* — F. T. Lewis has studied the 

 development of the pinnate leaves of the rose, blackberry, etc., and 

 emphasises the primary distinction between the basipetal and basifugal 

 types of growth. The author prefers, however, to separate the rose 

 from the basipetal class of leaves, and to classify it as " stipular " ; he 

 agrees with Trecul and Lubbock in regarding the rose stipules as of 

 earlier growth than the lateral leaflets. In cases where relatively simple 

 leaves occur on plants which bear lobed or compound forms, there 

 appears to be an arrest of development followed by expansion, or ex- 

 pansion before completion of the embryonic stage. The occurrence 

 of simpler leaves near cotyledons, bud-scales, and sepals may be the 

 outcome of rapidity of growth. 



Microcycas calocoma.f — 0. W. Caldwell contributes a second paper 

 on this genus with special reference to its habitat and morphology. In 

 Western Cuba small and widely scattered groups of Microcycas calocoma 

 are to be found. The adult plant reaches the greatest height and cir- 

 cumference yet attained by the indigenous Cycads of the Western 

 Hemisphere. The stem is straight or branched, and the ovulate cone is 

 the largest known, resembling that of Zamia. Unbranched vascular 

 bundles pass up the stalk of the megasporophyll ; they then anastomose, 

 finally branching repeatedly. The staminate cone is long and slender, 

 having numerous sporangia on the abaxial side of its sporophylls, but 

 there is no grouping into sori. In the male gametophyte eight body- 

 cells and sixteen sperms are formed, and each body-cell has two large 

 blepharoplasts. The female gametophyte is often lobed and may have 

 over 200 archegonia, which develop on any part of the surface or even 

 in the endosperm. Many embryos are formed, the suspensor being long 

 and coiled spirally so as to press the embryo-tip against the endosperm. 

 There are three to six cotyledons. Microcycas is the most primitive 

 Cycad yet described. 



Anatomy of Monocotyledons.^ — C. Queva, who recently published 

 his investigations upon the tuberous Uvularieae, now gives the results of 

 his studies of the rhizotomous members of the group. The two genera 

 studied by the author were Uvularia and Tricyrtis. The characters of 



* Amer. Nat., xli. (1907) pp. 431-41 (4 figs.). 



t Bot. Gazette, xliv. (1907) pp. 118-41 (2 pis. and 14 figs.). 



I Bot. Centralbl., xxii. (1907) pp. 30-77 (49 figs.). 



