ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 319 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 Including- Cell-Contents. 



Cytology in Relation to Genetics.* — E. B. "Wilson contributes a 

 paper dealing with some aspects of cytology in relation to genetics, in 

 which he endeavours to show that " the entire germinal complex is 

 directly or indirectly involved in the production of every character," 

 and that unit-characters are connected in some way with the combina- 

 tions, dissociations, and recombinations of diflferent chemical substances. 

 The author is of the opinion that, just as the addition or subtraction of 

 a molecular group may alter the organization of protein compounds, so 

 the addition or subtraction of some factor in the zygote calls forth 

 specific characters. Chromatin has been proved to be such a factor, and 

 its distribution occurs during mitosis. It is probable that similar factors 

 occur in the protoplasm, as is indicated by the presence of chondriosomes, 

 plastosomes, etc. Three facts appear to be very significant, viz. (1) 

 Chromosomes are proved to be compound bodies made up of different 

 constituents which undergo different modes of segregation in different 

 species ; (2) the spireme threads appear to affect a linear distribution of 

 different constituents in preparation for division or definite type of 

 association ; (3) chromosomes differ in their physiological relation to 

 development and are proljably one of the factors in sex-heredity. 



Identity of " Mitochondrias " and Leucoplasts.f — A. GuilHermond 

 contributes a further note upon the origin of starch. The experiments 

 were made in this instance upon the tubers of Phajus grandifoUus, and 

 they confirm the results obtained with the potato, although somewhat 

 modifying them. The " mitochondrias," which are most frequently rod- 

 like or spindle-shaped, produce the starch-grains upon any part of their 

 surface ; in some cases a single " mitochondria " may give rise to two or 

 more grains. The remains of the mitochondria adhere to the starch- 

 grain in the form of a tiny cap. All starch-grains appear to originate in 

 this way, including the transitory grains formed at the beginning of 

 germination. The " mitochondrias " appear to be identical with 

 Schimper's leucoplasts, and there is reason for regarding them as inde- 

 pendent organisms, at whose expense the products and secretions of the 

 cells are formed. 



Structure and Development. 

 Vegetative. 



American Fossil Cycads. VI.; — G. R. Wieland has studied the 

 flower-buds of Cycadeoidea, and in the present paper gives special atten- 



* Amer. Nat., xlvi. (1912) pp. 57-f.7. 



t Comptes Rendus, civ. (1911) pp. 286-9. 



X Amer. -Journ. Sci., xxxiii. (1912) pp. 73-91 (11 figs.). 



