SCIENCE. 



505* 



Studies of resting seeds belonging to sev- 

 eral genera and of germinating seeds indi- 

 cate that the nucleus of the resting seed is 

 homogeneous, with the exception of the 

 nucleolus in which the chromatin is aggre- 

 gated. As the nucleus passes from the 

 resting to the active state, the nucleolus 

 becomes vacuolated, and chromatin is grad- 

 ually given off by it and distributed in the 

 form of granules throughout the body of 

 the nucleus. These granules increase in size 

 and number and finally are aggregated to 

 form the spireme, which segments, as usual, 

 into chromosomes. The chromosomes do 

 not, therefore, retain their individuality 

 throughout the life-cycle of the organism, 

 and are not constantly present as the dif- 

 ferentiated bearers of the hereditary qual- 

 ities of the plant. 



The Recognition of Hybrid Characters in 

 the Structure of the Vascular Cylinder 

 as Expressed in the Genus Catalpa: 

 Professor D. P. Penhallow, McGill 

 University. (Presented in synopsis.) 

 In 1889 Professor C. S. Sargent pub- 

 lished an account of an interesting and 

 newly observed case of hybridization be- 

 tween two species of Catalpa which he de- 

 signated as Catalpa X J. C. Teas in refer- 

 ence to the origin of the tree in the nursery 

 of J\Ir. Teas of Carthage, Mo. The account 

 referred to states that Catalpa kaempferi 

 was planted in 1864 in a nursery contain- 

 ing C. speciosa and C. hignonioides. 

 Eventually the first species produced a 

 single pod of seeds which were wholly un- 

 like anything hitherto known. When 

 these seeds were planted they produced a 

 tree almost intermediate in character be- 

 tween C. kaempferi and one of the Ameri- 

 can species. Mr. Teas was of the opinion 

 that the cross was with C. speciosa, while 

 Professor Sargent considered C. hignonio- 

 ides as the other parent, basing his con- 

 clusions upon the fact that the flowers of 



C. speciosa were two to three weeks earlier 

 than those of C. kaempferi, while the 

 flowex's of C. hignonioides are ci ntenipo- 

 raneous with those of the Japanese species. 

 No other evidence has since been forthcom- 

 ing, so far as I am aware, and the real 

 American parentage of a most noteworthy 

 addition to the ornamental trees of this 

 country still remains in doubt. Within 

 the last twelve years, opportunities have 

 been presented to inquire into the evidence 

 which might be secured from an anatomical 

 point of view, and to determine to what 

 extent, if any, the external alterations 

 attendant upon hybridization were accom- 

 panied by corresponding internal struc- 

 tural changes. It was felt that the answer 

 to this question might very largely con- 

 tribute to a solution of the difficult prob- 

 lems relating to the origin of species, either 

 by mutation or by hybridization, and per- 

 mit of a more precise limitation of the 

 characters vrhich define a species. 



An examination of typical material 

 taken from the mature stem of the hybrid 

 and from each of the possible parents, 

 showed that the characters were to be most 

 clearly recognized in transverse and tan- 

 gential sections, especially in the former. 

 A very careful analysis of all the stmictural 

 features showed that out of a possible maxi- 

 mum of thirty-two, 34 per cent, were com- 

 mon to Catalpa speciosa only, and from 

 the well-defined characteristics which it ex- 

 hibited, it was possible to eliminate it from 

 further consideration and to definitely de- 

 termine that it could not be one of the 

 parents. On the other hand, it appeared 

 that there were 31 per cent, of characters 

 common to the hybrid, C. hignonioides and 

 C. kaempferi, while in the hybrid it was 

 also possible to determine features which 

 could not be accounted for except as the 

 resultant of action between C. kaempferi 

 and C. hignonioides. The evidence avail- 

 able shows that : 



