148 CANNON: STUDIES IN PLANT HysrRIpDs 
Gladiolus blandus Sol. of the lily family was fertilized with pollen 
of Hippeastrum sp. and seeds were formed that produced four 
hybrids, all of which were presumably sterile (Focke, /. c. 388). 
~~ The same author says that Digztals ambigua of the Scrophulari- 
aceae was crossed by Campbell with pollen of Siuningia speciosa 
of the Gloxiniaceae, and of the seeds that were formed only one 
produced a plant, and that one was sterile. The limits for any 
cross are thus set by related families, but as has already been 
shown the limits bounded by the fertility of the offspring are much 
narrower. 
STUDIES OF THE SPERMATOGENESIS AND STRUCTURE OF HyBRIDS 
A few morphological studies of hybrids have been made 
which may now be briefly referred to. I shall speak first of the 
work on the gametogenesis of hybrids. 
Juel * studied the spermatogenesis of Syringa Rothomagensts, 
and as a leading result found that the maturation mitoses were 
irregular and abnormal, although in some respects certain of the 
mitoses reported by him approach the usual or normal type. The 
abnormalities in the tetrad formation are classified and summarized 
by him as follows: 
A. In friiheren Entwickelungsstadien auftretend : 
1. Verkimmern der Pollenmutterzellen beim Eintritt 
des Spiremstadiums ; 
2. Durchschnirung des Kernes der Pollenmutterzelle im 
Spiremstadium ; 
B. Bei der Tetradentheilung auftretend : 
3. Durchschniirung der Kerne ; 
4. Erste Kerntheilung indirect, aber in Bezug auf das 
Verhalten der Chromosomen abnorm ; 
5. Achromatische Kernfigur abnorm ; 
6. Ein Theil des Chromatins im Cytoplasma zerstreut ; 
C. An den Tetraden beobachtet : 
7. Ueberzahlige Tetraden. Wahrscheinlich aus 2 hervor- 
gegangen. : 
8. Ueberschissige Kerne in den Zellen der Tetrade. 
Wahrscheinlich aus 6 hervorgegangen. 
*Juel, Beitrige zur Kenntniss der Tetradentheilung. 2. Die Tetradentheilung 
bei einer hybriden Pflanze. Jahrb. Wiss, Bot. 35: 638. 1900. 
