for systematic affinity includes resemblances of all kinds. First crosses between forms known to be varieties, or sufficiently alike to be considered as varieties, and their mongrel offspring, are very generally, but not, as is so often stated, invariably fertile.
Aldakitzat dauden edo halakotzat hartzeko bezain antzekoak diren formen arteko lehen gurutzaketak eta haien ondorengoen arteko gurutzaketak oso eskuarki, baina ez, sarri esan izan den moduan, hutsik gabe, ugalkorrak izaten dira.