The leftdown figure shows the interface of stem and first leave. Right to it is a broken baby spike, which might be growing into a small spike. The rightdown figure shows that there is a  round base under the baby spike connected to the stem, just like the spikes. This suports the assumption that the baby spike is the earlier stage of spikes. Also the small spike in previous webpage has similar shape like baby spike. The second right figure is the crosssection of the root before bean turns into seedling. Also, one can see baby spike and spikes growing in the firstleaf (leaf webpage), but not the epicoty - refer to the large assembling micrograph of leafl. Thus it seems that baby spike appears everwhere that is growing.  

By the way, baby spike looks like abdominal muscle in some sense.