Context :

Aims : To investigate the spectroscopic properties of a selected optical photospheric spectra of core collapse supernovae ( CCSNe ) .
Special attention is devoted to traces of hydrogen at early phases .
The impact on the physics and nature of their progenitors is emphasized .

Methods : The CCSNe-sample spectra are analyzed with the parameterized supernova synthetic spectrum code “ SYNOW ” adopting some simplifying approximations .

Results : The generated spectra are found to match the observed ones reasonably well , including a list of only 23 candidate ions .
Guided by SN Ib 1990I , the observed trough near 6300Å is attributed to H \alpha in almost all Type Ib events , although in some objects it becomes too weak to be discernible , especially at later phases .
Alternative line identifications are discussed .
Differences in the way hydrogen manifests its presence within CCSNe are highlighted .
In Type Ib SNe , the H \alpha contrast velocity ( i.e .
line velocity minus the photospheric velocity ) seems to increase with time at early epochs , reaching values as high as 8000 km s ^ { -1 } around 15 - 20 days after maximum and then remains almost constant .
The derived photospheric velocities , indicate a lower velocity for Type II SNe 1987A and 1999em as compared to SN Ic 1994I and SN IIb 1993J , while Type Ib events display a somewhat larger variation .
The scatter , around day 20 , is measured to be \sim 5000 km s ^ { -1 } .
Following two simple approaches , rough estimates of ejecta and hydrogen masses are given .
A mass of hydrogen of approximately 0.02 M _ { \odot } is obtained for SN 1990I , while SNe 1983N and 2000H ejected \sim 0.008 M _ { \odot } and \sim 0.08 M _ { \odot } of hydrogen , respectively .
SN 1993J has a higher hydrogen mass , \sim 0.7 M _ { \odot } with a large uncertainty .
A low mass and thin hydrogen layer with very high ejection velocities above the helium shell , is thus the most likely scenario for Type Ib SNe .
Some interesting and curious issues relating to oxygen lines suggest future investigations .

Conclusions :