Pic2

hopefully you can see in this example. Some of them I swear are flat like shoelaces.

They look like squash/zuke seedlings that are very elongated getting uneven watering and not enough direct sun causing them to split.

The change in the leaf stems give them a higher surface area to volume ratio, which would make them more efficient at expelling and evaporating water. It would do this either to rid itelf of harmful ammounts of water, or to cool the plant, or a combination of both.

However, leaves (foiliage) woud be naturally more efficient at these tasks than stems. So maybe something on the leaves like naturally occurring wax, or a build-up of sprays and dust, could be blocking the leaves from efficiently evaporating. Maybe hosing them down good with a light soap (quickly-you don't want to soak them if they are alteady too wet.) Good luck, and remember that new squash plants grow very quickly (from seed) and may be your easiest way out of this problem.
-Terry

This post was edited by terry_neoh on Thu, May 1, 14 at 6:12

Flat, markedly elongated, and split stems are caused by a severe insufficiency of the needed light if grown indoors or sun if grown outdoors. You don't indicate where growing - in or out. Their color is also an indication of very poor light/sun exposure.

Ambient air temps can contribute to the problem but since you give no indication of your location or zone I can't comment on how that could have contributed in this case.

These seedlings are not salvageable.

Dave