JANUABT 29, 1915] 



SCIENCE 



183 



somes on the thin threads to which they were at- 

 tached before synapsis began, the contents of the 

 two individuals of a pair flowing in opposite di- 

 rections. 



As the growth period advances these threads 

 enlarge, become less entangled, and the splitting 

 becomes more apparent. At this stag& deeper 

 staining bodies of different sizes are found dis- 

 tributed on the threads; these bodies, possibly 

 chromomeres, are always found in pairs, one on 

 each of the two parts of the double thread. 

 There are usually 3 or 4 pairs of these chromo- 

 meres on each of the bivalent threads, the indi- 

 viduals of each pair being opposite each other and 

 equal in size. As these bivalent threads become 

 less entangled the number of the threads is found 

 to be 13, one half the number of prochromosomes 

 observed before synapsis. The details from this 

 stage on have not as yet been worked out, but ob- 

 servations indicate that each of these 13 threads 

 becomes shorter and finally forms a bivalent chro- 

 mosome. 



In the first division of the nucleus 13 chromo- 

 somes pass to each pole; in the reconstructed 

 daughter nucleus 13 prochromosomes appear, but 

 these are not arranged in pairs. In the resting 

 nuclei of the somatic tissue the prochromosomes 

 are present and appear to be more or less in pairs. 



These observations seem to show that in Acer 

 ylatanoides prochromosomes exist in the nucleus; 

 that they are arranged more or less in pairs in 

 both somatic and mother cells; that in synapsis 

 the members of each pair unite and form a thick 

 thread on the single thread which preceded 

 synapsis; that this single thick thread becomes 

 split longitudinally; that upon this bivalent thread 

 occur paired chromomeres; and finally that each 

 bivalent thread becomes a bivalent chromosome 

 which divides into univalent chromosomes in the 

 first division of the pollen mother cell. 

 Cytology of Sphwroplea: E. M. Gilbert. 



Cleavage begins with constrictions from the 

 plasma membrane, and the cell contents are cut 

 into masses of varying sizes. A single row of 

 large cells or a double row of smaller cells may 

 be found in a single filament. 



All eggs at first contain more than a single 

 nucleus, and all but one of these disappears be- 

 fore the egg is fully mature. 



Nuclear divisions as far as observed are mi- 

 totic and no indications of amitotic divisions, de- 

 scribed by earlier investigators, have been found. 

 There is no fragmentation of the nucleole to form 

 the chromosomes. 



The number of pyrenoids found in eggs varies 

 from two to seven. 



The pyrenoids vary greatly in size and each is 

 made up of a varying number of segments. The 

 starch is usually laid down around the pyrenoid 

 in definite layers but at times the arrangement is 

 very irregular. Stromatie starch is very abun- 

 dant in some mature eggs. 



The pyrenoids disappear from portions of fila- 

 ment which are active in the formation of sperms. 



Fertilization does not take place until the egg is 

 fully formed and rounded; at this time the egg 

 nucleus lies in the center of the egg. 



An Anatomical Study of the Boot of Ipomcea 



'batatas: Floeence A. McCormick. 



A preliminary paper on the anatomy of Ipomaea 

 batatas. During the investigation, a fungus, sim- 

 ilar to the one found in Solanum tuberosum has 

 been found in the endodermis of the root, but so 

 far the fungus has not been seen in the stem. 



The Anatomy of a Protomyces Gall: Alban Stew- 

 art. 



The lower parts of the stems of Ambrosia 

 trifida L. are often attacked by Protomyces andi- 

 mis Lagh, causing considerable disturbance in the 

 tissues of the host. Large swellings are caused by 

 this parasite, one or more of which may appear 

 on the same plant. 



Sections of these galls show, among other things, 

 an increase in the tissues of the bark, an abnormal 

 growth of the fibrovascular bundles as compared 

 with non-infected parts close by, a broadening of 

 the rays and the formation of other parenchyma 

 elements in the bundles, areas of cambiform cells 

 in the pith. 



A gall caused by an unknown insect, probably 

 of the order Lepidoptera, also occurs on the stems 

 of this species of Ambrosia. The changes induced 

 by this insect in the tissues of the host are simi- 

 lar in certain respects to those caused by Proto- 

 myces. 

 The Anatomy of the Punctatus Gall: Alban 



Stewart. 



Andrious punctatus Bass., a hymenopterous in- 

 sect of the family Cynipida?, causes large woody 

 galls on the stems and branches of Quercus vehi- 

 tina Lam. and other closely related species of 

 oak. This gall possesses, among others, the fol- 

 lowing anatomical characters which are of especial 

 interest. 



A recapitulation of a similar condition of ray 

 structure to that which occurs in traumatic wood 



