EDIT

  .block-cdm-dataportal-feature,  .media-caption, .specimens { // TODO .specimens may be obsolete

  // derivatives tree view (see also derivation-tree.js)

  $tree-entry-vspace: 0; //$base-font-size / 10; TODO remove

  $tree-line-style: 3px solid $tabs-border;

  $tree-lines-top-offset: $base-line-height / 7;

  $tree-lines-left-offset: $base-line-height / 7;

  div.derived-unit-tree,

  ul.derived-unit-sub-tree,

  ul.derived-unit-sub-tree ul {

    list-style: none;

    margin: 0 0 0 $tree-lines-left-offset;

    padding: 0;

    .unit-content {

      background-color: $menu-bar-background-color;

      margin-left: 1em;

    }

   .unit-label {

      cursor: pointer;

    }

    .unit-label:hover {

      background-color: $menu-bar-background-color;

    }

  }

  div.derived-unit-tree-root {

    .unit-content-wrapper {

      border-left: $tree-line-style;

      margin-left: $tree-lines-left-offset;

    }

    div.item-list { // class .item-list is defined by drupal theme function

      margin-top: $tree-lines-top-offset;

    }

  }

  ul.derived-unit-sub-tree{

    ul {

      margin-left: 1.0em;

    }

    li {

      position: relative;

      margin-left: 0;

      padding-left: 1em;

      margin-top: -$tree-lines-top-offset;

      margin-bottom: $tree-entry-vspace;

      line-height: $base-line-height;

      border-left: $tree-line-style;

    }

    li:last-child {

      border-left: none;

    }

    li:before {

      position: absolute;

      top: $tree-lines-top-offset;

      left: 0;

      width: 0.5em; /* width of horizontal line */

      height: 0.5em; /* vertical position of line */

      vertical-align: top;

      border-bottom: $tree-line-style;

      content: "";

      display: inline-block;

    }

    li:last-child:before {

      border-left: $tree-line-style;

    }

  }